From 9f4ac2c2dcee7fd1b708f5f0b3d6c5832638fb57 Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Mon, 21 Nov 2016 23:55:55 +0000
Subject: [PATCH 01/25] efi: Add EFI_SECURE_BOOT bit

UEFI machines can be booted in Secure Boot mode.  Add a EFI_SECURE_BOOT bit
that can be passed to efi_enabled() to find out whether secure boot is
enabled.

This will be used by the SysRq+x handler, registered by the x86 arch, to find
out whether secure boot mode is enabled so that it can be disabled.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 arch/x86/kernel/setup.c | 1 +
 include/linux/efi.h     | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 3486d04988000b..319995f5834562 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1190,6 +1190,7 @@ void __init setup_arch(char **cmdline_p)
 			pr_info("Secure boot disabled\n");
 			break;
 		case efi_secureboot_mode_enabled:
+			set_bit(EFI_SECURE_BOOT, &efi.flags);
 			pr_info("Secure boot enabled\n");
 			break;
 		default:
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 8269bcb8ccf796..7952dd3ffa7378 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1081,6 +1081,7 @@ extern int __init efi_setup_pcdp_console(char *);
 #define EFI_DBG			8	/* Print additional debug info at runtime */
 #define EFI_NX_PE_DATA		9	/* Can runtime data regions be mapped non-executable? */
 #define EFI_MEM_ATTR		10	/* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */
+#define EFI_SECURE_BOOT		11	/* Are we in Secure Boot mode? */
 
 #ifdef CONFIG_EFI
 /*

From f7364eee64c715ffe9266d8ea55d52154becf879 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Mon, 21 Nov 2016 23:36:17 +0000
Subject: [PATCH 02/25] Add the ability to lock down access to the running
 kernel image

Provide a single call to allow kernel code to determine whether the system
should be locked down, thereby disallowing various accesses that might
allow the running kernel image to be changed including the loading of
modules that aren't validly signed with a key we recognise, fiddling with
MSR registers and disallowing hibernation,

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/linux/kernel.h   |  9 +++++++++
 include/linux/security.h | 11 +++++++++++
 security/Kconfig         | 15 +++++++++++++++
 security/Makefile        |  3 +++
 security/lock_down.c     | 40 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 78 insertions(+)
 create mode 100644 security/lock_down.c

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index bd6d96cf80b17c..65692c80aa1a3f 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -277,6 +277,15 @@ extern int oops_may_print(void);
 void do_exit(long error_code) __noreturn;
 void complete_and_exit(struct completion *, long) __noreturn;
 
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern bool kernel_is_locked_down(void);
+#else
+static inline bool kernel_is_locked_down(void)
+{
+	return false;
+}
+#endif
+
 /* Internal, do not use. */
 int __must_check _kstrtoul(const char *s, unsigned int base, unsigned long *res);
 int __must_check _kstrtol(const char *s, unsigned int base, long *res);
diff --git a/include/linux/security.h b/include/linux/security.h
index b6ea1dc9cc9d2b..834b355fa298fd 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1764,5 +1764,16 @@ static inline void free_secdata(void *secdata)
 { }
 #endif /* CONFIG_SECURITY */
 
+#ifdef CONFIG_LOCK_DOWN_KERNEL
+extern void lock_kernel_down(void);
+#ifdef CONFIG_ALLOW_LOCKDOWN_LIFT
+extern void lift_kernel_lockdown(void);
+#endif
+#else
+static inline void lock_kernel_down(void)
+{
+}
+#endif
+
 #endif /* ! __LINUX_SECURITY_H */
 
diff --git a/security/Kconfig b/security/Kconfig
index e8e449444e658b..1a84ed33c09a33 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -205,6 +205,21 @@ config STATIC_USERMODEHELPER_PATH
 	  If you wish for all usermode helper programs to be disabled,
 	  specify an empty string here (i.e. "").
 
+config LOCK_DOWN_KERNEL
+	bool "Allow the kernel to be 'locked down'"
+	help
+	  Allow the kernel to be locked down under certain circumstances, for
+	  instance if UEFI secure boot is enabled.  Locking down the kernel
+	  turns off various features that might otherwise allow access to the
+	  kernel image (eg. setting MSR registers).
+
+config ALLOW_LOCKDOWN_LIFT
+	bool
+	help
+	  Allow the lockdown on a kernel to be lifted, thereby restoring the
+	  ability of userspace to access the kernel image (eg. by SysRq+x under
+	  x86).
+
 source security/selinux/Kconfig
 source security/smack/Kconfig
 source security/tomoyo/Kconfig
diff --git a/security/Makefile b/security/Makefile
index f2d71cdb8e19b1..8c4a43e3d4e030 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -29,3 +29,6 @@ obj-$(CONFIG_CGROUP_DEVICE)		+= device_cgroup.o
 # Object integrity file lists
 subdir-$(CONFIG_INTEGRITY)		+= integrity
 obj-$(CONFIG_INTEGRITY)			+= integrity/
+
+# Allow the kernel to be locked down
+obj-$(CONFIG_LOCK_DOWN_KERNEL)		+= lock_down.o
diff --git a/security/lock_down.c b/security/lock_down.c
new file mode 100644
index 00000000000000..5788c60ff4e17b
--- /dev/null
+++ b/security/lock_down.c
@@ -0,0 +1,40 @@
+/* Lock down the kernel
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/security.h>
+#include <linux/export.h>
+
+static __read_mostly bool kernel_locked_down;
+
+/*
+ * Put the kernel into lock-down mode.
+ */
+void lock_kernel_down(void)
+{
+	kernel_locked_down = true;
+}
+
+/*
+ * Take the kernel out of lockdown mode.
+ */
+void lift_kernel_lockdown(void)
+{
+	kernel_locked_down = false;
+}
+
+/**
+ * kernel_is_locked_down - Find out if the kernel is locked down
+ */
+bool kernel_is_locked_down(void)
+{
+	return kernel_locked_down;
+}
+EXPORT_SYMBOL(kernel_is_locked_down);

From c3b1b1051e324f57e37254563bb7364a350efeb1 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Mon, 21 Nov 2016 23:55:55 +0000
Subject: [PATCH 03/25] efi: Lock down the kernel if booted in secure boot mode

UEFI Secure Boot provides a mechanism for ensuring that the firmware will
only load signed bootloaders and kernels.  Certain use cases may also
require that all kernel modules also be signed.  Add a configuration option
that to lock down the kernel - which includes requiring validly signed
modules - if the kernel is secure-booted.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 arch/x86/Kconfig        | 12 ++++++++++++
 arch/x86/kernel/setup.c |  8 +++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 323cb065be5eda..8e41d54d649892 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1836,6 +1836,18 @@ config EFI_MIXED
 
 	   If unsure, say N.
 
+config EFI_SECURE_BOOT_LOCK_DOWN
+	def_bool n
+	depends on EFI
+	prompt "Lock down the kernel when UEFI Secure Boot is enabled"
+	---help---
+	  UEFI Secure Boot provides a mechanism for ensuring that the firmware
+	  will only load signed bootloaders and kernels.  Certain use cases may
+	  also require that all kernel modules also be signed and that
+	  userspace is prevented from directly changing the running kernel
+	  image.  Say Y here to automatically lock down the kernel when a
+	  system boots with UEFI Secure Boot enabled.
+
 config SECCOMP
 	def_bool y
 	prompt "Enable seccomp to safely compute untrusted bytecode"
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 319995f5834562..d0128aef43ce84 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -69,6 +69,7 @@
 #include <linux/crash_dump.h>
 #include <linux/tboot.h>
 #include <linux/jiffies.h>
+#include <linux/security.h>
 
 #include <linux/usb/xhci-dbgp.h>
 #include <video/edid.h>
@@ -1191,7 +1192,12 @@ void __init setup_arch(char **cmdline_p)
 			break;
 		case efi_secureboot_mode_enabled:
 			set_bit(EFI_SECURE_BOOT, &efi.flags);
-			pr_info("Secure boot enabled\n");
+			if (IS_ENABLED(CONFIG_EFI_SECURE_BOOT_LOCK_DOWN)) {
+				lock_kernel_down();
+				pr_info("Secure boot enabled and kernel locked down\n");
+			} else {
+				pr_info("Secure boot enabled\n");
+			}
 			break;
 		default:
 			pr_info("Secure boot could not be determined\n");

From d8d614fed5891ec1891e963d99396318c4a04045 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 23 Nov 2016 13:22:22 +0000
Subject: [PATCH 04/25] Enforce module signatures if the kernel is locked down

If the kernel is locked down, require that all modules have valid
signatures that we can verify.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/module.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/module.c b/kernel/module.c
index 40f983cbea81d1..e5b878b2690678 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2781,7 +2781,7 @@ static int module_sig_check(struct load_info *info, int flags)
 	}
 
 	/* Not having a signature is only an error if we're strict. */
-	if (err == -ENOKEY && !sig_enforce)
+	if (err == -ENOKEY && !sig_enforce && !kernel_is_locked_down())
 		err = 0;
 
 	return err;

From 297df5adbc6430dccc8c7e37a296767551ce59d0 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 05/25] Restrict /dev/mem and /dev/kmem when the kernel is
 locked down

Allowing users to write to address space makes it possible for the kernel to
be subverted, avoiding module loading restrictions.  Prevent this when the
kernel has been locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/char/mem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 593a8818aca99e..ba68add9677f43 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -179,6 +179,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	if (p != *ppos)
 		return -EFBIG;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (!valid_phys_addr_range(p, count))
 		return -EFAULT;
 
@@ -540,6 +543,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
 	char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 	int err = 0;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (p < (unsigned long) high_memory) {
 		unsigned long to_write = min_t(unsigned long, count,
 					       (unsigned long)high_memory - p);

From b61a37800ef46d9849b6d783bcba5818ec50f821 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 06/25] kexec: Disable at runtime if the kernel is locked down

kexec permits the loading and execution of arbitrary code in ring 0, which
is something that lock-down is meant to prevent. It makes sense to disable
kexec in this situation.

This does not affect kexec_file_load() which can check for a signature on the
image to be booted.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/kexec.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index e62ec4dc662060..37f75d0b75deb9 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -201,6 +201,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
 
+	/*
+	 * kexec can be used to circumvent module loading restrictions, so
+	 * prevent loading in that case
+	 */
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	/*
 	 * Verify we have a legal set of flags
 	 * This leaves us room for future extensions.

From e52bc57b6b14801e7b5bbd33d53d43a6020449d4 Mon Sep 17 00:00:00 2001
From: Dave Young <dyoung@redhat.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 07/25] Copy secure_boot flag in boot params across kexec
 reboot

Kexec reboot in case secure boot being enabled does not keep the secure
boot mode in new kernel, so later one can load unsigned kernel via legacy
kexec_load.  In this state, the system is missing the protections provided
by secure boot.

Adding a patch to fix this by retain the secure_boot flag in original
kernel.

secure_boot flag in boot_params is set in EFI stub, but kexec bypasses the
stub.  Fixing this issue by copying secure_boot flag across kexec reboot.

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index fb095ba0c02fb0..7d0fac5bcbbe46 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -179,6 +179,7 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
 	if (efi_enabled(EFI_OLD_MEMMAP))
 		return 0;
 
+	params->secure_boot = boot_params.secure_boot;
 	ei->efi_loader_signature = current_ei->efi_loader_signature;
 	ei->efi_systab = current_ei->efi_systab;
 	ei->efi_systab_hi = current_ei->efi_systab_hi;

From c968d5f727c6e920190b32773dcff484eb10e738 Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>
Date: Wed, 23 Nov 2016 13:49:19 +0000
Subject: [PATCH 08/25] kexec_file: Disable at runtime if securelevel has been
 set

When KEXEC_VERIFY_SIG is not enabled, kernel should not loads image
through kexec_file systemcall if securelevel has been set.

This code was showed in Matthew's patch but not in git:
https://lkml.org/lkml/2015/3/13/778

Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/kexec_file.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 9f48f441229720..7da87007c20266 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -255,6 +255,12 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
 
+	/* Don't permit images to be loaded into trusted kernels if we're not
+	 * going to verify the signature on them
+	 */
+	if (!IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG) && kernel_is_locked_down())
+		return -EPERM;
+
 	/* Make sure we have a legal set of flags */
 	if (flags != (flags & KEXEC_FILE_FLAGS))
 		return -EINVAL;

From a936ae2a13f552c581c7a467cb64695d00beac7d Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@fedoraproject.org>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 09/25] hibernate: Disable when the kernel is locked down

There is currently no way to verify the resume image when returning
from hibernate.  This might compromise the signed modules trust model,
so until we can work with signed hibernate images we disable it when the
kernel is locked down.

Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/power/hibernate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index e1914c7b85b180..7859ba79e1813d 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -70,7 +70,7 @@ static const struct platform_hibernation_ops *hibernation_ops;
 
 bool hibernation_available(void)
 {
-	return (nohibernate == 0);
+	return nohibernate == 0 && !kernel_is_locked_down();
 }
 
 /**

From 40952a62add2d26d51d2c6ed8f16cf59ef376468 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <mjg59@srcf.ucam.org>
Date: Wed, 23 Nov 2016 13:28:17 +0000
Subject: [PATCH 10/25] uswsusp: Disable when the kernel is locked down

uswsusp allows a user process to dump and then restore kernel state, which
makes it possible to modify the running kernel.  Disable this if the kernel
is locked down.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/power/user.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 22df9f7ff67242..e4b926d329b797 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -52,6 +52,9 @@ static int snapshot_open(struct inode *inode, struct file *filp)
 	if (!hibernation_available())
 		return -EPERM;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	lock_system_sleep();
 
 	if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {

From 0233bf96a5a3399bc35f118682c70fd82e272e19 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:15 +0000
Subject: [PATCH 11/25] PCI: Lock down BAR access when the kernel is locked
 down

Any hardware that can potentially generate DMA has to be locked down in
order to avoid it being possible for an attacker to modify kernel code,
allowing them to circumvent disabled module loading or module signing.
Default to paranoid - in future we can potentially relax this for
sufficiently IOMMU-isolated devices.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/pci/pci-sysfs.c | 9 +++++++++
 drivers/pci/proc.c      | 8 +++++++-
 drivers/pci/syscall.c   | 2 +-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 2f3780b5072367..534d6df4aec238 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -881,6 +881,9 @@ static ssize_t pci_write_config(struct file *filp, struct kobject *kobj,
 	loff_t init_off = off;
 	u8 *data = (u8 *) buf;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (off > dev->cfg_size)
 		return 0;
 	if (off + count > dev->cfg_size) {
@@ -1175,6 +1178,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
 	enum pci_mmap_state mmap_type;
 	struct resource *res = &pdev->resource[bar];
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
 
@@ -1258,6 +1264,9 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
 				     struct bin_attribute *attr, char *buf,
 				     loff_t off, size_t count)
 {
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	return pci_resource_io(filp, kobj, attr, buf, off, count, true);
 }
 
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 098360d7ff8163..ef16fccb192353 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -116,6 +116,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const char __user *buf,
 	int size = dev->cfg_size;
 	int cnt;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (pos >= size)
 		return 0;
 	if (nbytes >= size)
@@ -195,6 +198,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
 #endif /* HAVE_PCI_MMAP */
 	int ret = 0;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	switch (cmd) {
 	case PCIIOC_CONTROLLER:
 		ret = pci_domain_nr(dev->bus);
@@ -236,7 +242,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
 	struct pci_filp_private *fpriv = file->private_data;
 	int i, ret, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-	if (!capable(CAP_SYS_RAWIO))
+	if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
 		return -EPERM;
 
 	if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index 9bf993e1f71e83..c09524738ceba6 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -92,7 +92,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
 	u32 dword;
 	int err = 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!capable(CAP_SYS_ADMIN) || kernel_is_locked_down())
 		return -EPERM;
 
 	dev = pci_get_bus_and_slot(bus, dfn);

From 1cee6d2ec1ce531436d0224c881bf6c881bfedad Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 12/25] x86: Lock down IO port access when the kernel is locked
 down

IO port access would permit users to gain access to PCI configuration
registers, which in turn (on a lot of hardware) give access to MMIO
register space. This would potentially permit root to trigger arbitrary
DMA, so lock it down by default.

This also implicitly locks down the KDADDIO, KDDELIO, KDENABIO and
KDDISABIO console ioctls.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 arch/x86/kernel/ioport.c | 4 ++--
 drivers/char/mem.c       | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c
index 9c3cf0944bce35..4a613fed94b654 100644
--- a/arch/x86/kernel/ioport.c
+++ b/arch/x86/kernel/ioport.c
@@ -30,7 +30,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on)
 
 	if ((from + num <= from) || (from + num > IO_BITMAP_BITS))
 		return -EINVAL;
-	if (turn_on && !capable(CAP_SYS_RAWIO))
+	if (turn_on && (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down()))
 		return -EPERM;
 
 	/*
@@ -120,7 +120,7 @@ SYSCALL_DEFINE1(iopl, unsigned int, level)
 		return -EINVAL;
 	/* Trying to gain more privileges? */
 	if (level > old) {
-		if (!capable(CAP_SYS_RAWIO))
+		if (!capable(CAP_SYS_RAWIO) || kernel_is_locked_down())
 			return -EPERM;
 	}
 	regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) |
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index ba68add9677f43..5e2a260fb89fb0 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -768,6 +768,8 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
 
 static int open_port(struct inode *inode, struct file *filp)
 {
+	if (kernel_is_locked_down())
+		return -EPERM;
 	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 }
 

From 6259908d97b6fddd8df26b725526386ee4519be7 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:17 +0000
Subject: [PATCH 13/25] x86: Restrict MSR access when the kernel is locked down

Writing to MSRs should not be allowed if the kernel is locked down, since
it could lead to execution of arbitrary code in kernel mode.  Based on a
patch by Kees Cook.

Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 arch/x86/kernel/msr.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index ef688804f80d33..fbcce028e502f3 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
 	int err = 0;
 	ssize_t bytes = 0;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (count % 8)
 		return -EINVAL;	/* Invalid chunk size */
 
@@ -131,6 +134,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
 			err = -EBADF;
 			break;
 		}
+		if (kernel_is_locked_down()) {
+			err = -EPERM;
+			break;
+		}
 		if (copy_from_user(&regs, uregs, sizeof regs)) {
 			err = -EFAULT;
 			break;

From b58e91fc00f8d64b56535e728f766aa61c09395e Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 14/25] asus-wmi: Restrict debugfs interface when the kernel is
 locked down

We have no way of validating what all of the Asus WMI methods do on a given
machine - and there's a risk that some will allow hardware state to be
manipulated in such a way that arbitrary code can be executed in the
kernel, circumventing module loading restrictions.  Prevent that if the
kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/platform/x86/asus-wmi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 709e3a67391a0b..2d8db47698b2d4 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -1905,6 +1905,9 @@ static int show_dsts(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval);
 
 	if (err < 0)
@@ -1921,6 +1924,9 @@ static int show_devs(struct seq_file *m, void *data)
 	int err;
 	u32 retval = -1;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param,
 				    &retval);
 
@@ -1945,6 +1951,9 @@ static int show_call(struct seq_file *m, void *data)
 	union acpi_object *obj;
 	acpi_status status;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID,
 				     1, asus->debug.method_id,
 				     &input, &output);

From 5fab1bc15838e14d65b5cf0c345180e0f31299f4 Mon Sep 17 00:00:00 2001
From: Matthew Garrett <matthew.garrett@nebula.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 15/25] ACPI: Limit access to custom_method when the kernel is
 locked down

custom_method effectively allows arbitrary access to system memory, making
it possible for an attacker to circumvent restrictions on module loading.
Disable it if the kernel is locked down.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/acpi/custom_method.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index c68e72414a67a9..e4d721c330c079 100644
--- a/drivers/acpi/custom_method.c
+++ b/drivers/acpi/custom_method.c
@@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf,
 	struct acpi_table_header table;
 	acpi_status status;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	if (!(*ppos)) {
 		/* parse the table header to get the table length */
 		if (count <= sizeof(struct acpi_table_header))

From 0c833f13d477afe9980fad67e8eea8b0be8ab02d Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer@redhat.com>
Date: Tue, 22 Nov 2016 08:46:16 +0000
Subject: [PATCH 16/25] acpi: Ignore acpi_rsdp kernel param when the kernel has
 been locked down

This option allows userspace to pass the RSDP address to the kernel, which
makes it possible for a user to circumvent any restrictions imposed on
loading modules.  Ignore the option when the kernel is locked down.

Signed-off-by: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/acpi/osl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index db78d353bab1f9..d4d4ba3484510f 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -192,7 +192,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 	acpi_physical_address pa = 0;
 
 #ifdef CONFIG_KEXEC
-	if (acpi_rsdp)
+	if (acpi_rsdp && !kernel_is_locked_down())
 		return acpi_rsdp;
 #endif
 

From aeacbb5b071f36b680a1a726fe4cddd151ac3138 Mon Sep 17 00:00:00 2001
From: Linn Crosetto <linn@hpe.com>
Date: Wed, 23 Nov 2016 13:32:27 +0000
Subject: [PATCH 17/25] acpi: Disable ACPI table override if the kernel is
 locked down

From the kernel documentation (initrd_table_override.txt):

  If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible
  to override nearly any ACPI table provided by the BIOS with an
  instrumented, modified one.

When securelevel is set, the kernel should disallow any unauthenticated
changes to kernel space.  ACPI tables contain code invoked by the kernel,
so do not allow ACPI tables to be overridden if the kernel is locked down.

Signed-off-by: Linn Crosetto <linn@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/acpi/tables.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index ff425390bfa8d2..c72bfa97888ab0 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -526,6 +526,11 @@ void __init acpi_table_upgrade(void)
 	if (table_nr == 0)
 		return;
 
+	if (kernel_is_locked_down()) {
+		pr_notice("kernel is locked down, ignoring table override\n");
+		return;
+	}
+
 	acpi_tables_addr =
 		memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,
 				       all_tables_size, PAGE_SIZE);

From 6861bab3ed1d0b05bbac760b02b141067231f8ed Mon Sep 17 00:00:00 2001
From: Linn Crosetto <linn@hpe.com>
Date: Wed, 23 Nov 2016 13:39:41 +0000
Subject: [PATCH 18/25] acpi: Disable APEI error injection if the kernel is
 locked down

ACPI provides an error injection mechanism, EINJ, for debugging and testing
the ACPI Platform Error Interface (APEI) and other RAS features.  If
supported by the firmware, ACPI specification 5.0 and later provide for a
way to specify a physical memory address to which to inject the error.

Injecting errors through EINJ can produce errors which to the platform are
indistinguishable from real hardware errors.  This can have undesirable
side-effects, such as causing the platform to mark hardware as needing
replacement.

While it does not provide a method to load unauthenticated privileged code,
the effect of these errors may persist across reboots and affect trust in
the underlying hardware, so disable error injection through EINJ if
the kernel is locked down.

Signed-off-by: Linn Crosetto <linn@hpe.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/acpi/apei/einj.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
index ec50c32ea3da04..e082718d01c2b3 100644
--- a/drivers/acpi/apei/einj.c
+++ b/drivers/acpi/apei/einj.c
@@ -518,6 +518,9 @@ static int einj_error_inject(u32 type, u32 flags, u64 param1, u64 param2,
 	int rc;
 	u64 base_addr, size;
 
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	/* If user manually set "flags", make sure it is legal */
 	if (flags && (flags &
 		~(SETWA_FLAGS_APICID|SETWA_FLAGS_MEM|SETWA_FLAGS_PCIE_SBDF)))

From 6923d52b5ff758b74f0eec2129eb0b50f688285c Mon Sep 17 00:00:00 2001
From: "Lee, Chun-Yi" <jlee@suse.com>
Date: Wed, 23 Nov 2016 13:52:16 +0000
Subject: [PATCH 19/25] bpf: Restrict kernel image access functions when the
 kernel is locked down

There are some bpf functions can be used to read kernel memory:
bpf_probe_read, bpf_probe_write_user and bpf_trace_printk.  These allow
private keys in kernel memory (e.g. the hibernation image signing key) to
be read by an eBPF program.  Prohibit those functions when the kernel is
locked down.

Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 kernel/trace/bpf_trace.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index dc498b605d5dd3..fb240222b89b9a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
 {
 	int ret;
 
+	if (kernel_is_locked_down()) {
+		memset(dst, 0, size);
+		return -EPERM;
+	}
+
 	ret = probe_kernel_read(dst, unsafe_ptr, size);
 	if (unlikely(ret < 0))
 		memset(dst, 0, size);
@@ -84,6 +89,9 @@ static const struct bpf_func_proto bpf_probe_read_proto = {
 BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
 	   u32, size)
 {
+	if (kernel_is_locked_down())
+		return -EPERM;
+
 	/*
 	 * Ensure we're in user context which is safe for the helper to
 	 * run. This helper has no business in a kthread.
@@ -143,6 +151,9 @@ BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
 	if (fmt[--fmt_size] != 0)
 		return -EINVAL;
 
+	if (kernel_is_locked_down())
+		return __trace_printk(1, fmt, 0, 0, 0);
+
 	/* check format string for allowed specifiers */
 	for (i = 0; i < fmt_size; i++) {
 		if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))

From a710df0f8e65d1695ea3ea66aad01ed5ddba3757 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Tue, 22 Nov 2016 10:10:34 +0000
Subject: [PATCH 20/25] scsi: Lock down the eata driver

When the kernel is running in secure boot mode, we lock down the kernel to
prevent userspace from modifying the running kernel image.  Whilst this
includes prohibiting access to things like /dev/mem, it must also prevent
access by means of configuring driver modules in such a way as to cause a
device to access or modify the kernel image.

The eata driver takes a single string parameter that contains a slew of
settings, including hardware resource configuration.  Prohibit use of the
parameter if the kernel is locked down.

Suggested-by: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dario Ballabio <ballabio_dario@emc.com>
cc: "James E.J. Bottomley" <jejb@linux.vnet.ibm.com>
cc: "Martin K. Petersen" <martin.petersen@oracle.com>
cc: linux-scsi@vger.kernel.org
---
 drivers/scsi/eata.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/eata.c b/drivers/scsi/eata.c
index 227dd2c2ec2f16..5c036d10c18b8a 100644
--- a/drivers/scsi/eata.c
+++ b/drivers/scsi/eata.c
@@ -1552,8 +1552,13 @@ static int eata2x_detect(struct scsi_host_template *tpnt)
 
 	tpnt->proc_name = "eata2x";
 
-	if (strlen(boot_options))
+	if (strlen(boot_options)) {
+		if (kernel_is_locked_down()) {
+			pr_err("Command line-specified device addresses, irqs and dma channels are not permitted when the kernel is locked down\n");
+			return -EPERM;
+		}
 		option_setup(boot_options);
+	}
 
 #if defined(MODULE)
 	/* io_port could have been modified when loading as a module */

From 8b70741cefc743bff2cdead568980f510c0044ab Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 25 Nov 2016 14:37:45 +0000
Subject: [PATCH 21/25] Prohibit PCMCIA CIS storage when the kernel is locked
 down

Prohibit replacement of the PCMCIA Card Information Structure when the
kernel is locked down.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/pcmcia/cistpl.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/pcmcia/cistpl.c b/drivers/pcmcia/cistpl.c
index 55ef7d1fd8da13..193e4f7b73b1d4 100644
--- a/drivers/pcmcia/cistpl.c
+++ b/drivers/pcmcia/cistpl.c
@@ -1578,6 +1578,11 @@ static ssize_t pccard_store_cis(struct file *filp, struct kobject *kobj,
 	struct pcmcia_socket *s;
 	int error;
 
+	if (kernel_is_locked_down()) {
+		pr_err("Direct CIS storage isn't permitted when the kernel is locked down\n");
+		return -EPERM;
+	}
+
 	s = to_socket(container_of(kobj, struct device, kobj));
 
 	if (off)

From 47daa615c56f5b23928028a2e7b0b3c46bed80a0 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Wed, 7 Dec 2016 10:28:39 +0000
Subject: [PATCH 22/25] Lock down TIOCSSERIAL

Lock down TIOCSSERIAL as that can be used to change the ioport and irq
settings on a serial port.  This only appears to be an issue for the serial
drivers that use the core serial code.  All other drivers seem to either
ignore attempts to change port/irq or give an error.

Reported-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David Howells <dhowells@redhat.com>
---
 drivers/tty/serial/serial_core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index f534a40aebdeea..e32c0179f423c4 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -821,6 +821,12 @@ static int uart_set_info(struct tty_struct *tty, struct tty_port *port,
 	new_flags = new_info->flags;
 	old_custom_divisor = uport->custom_divisor;
 
+	if ((change_port || change_irq) && kernel_is_locked_down()) {
+		pr_err("Using TIOCSSERIAL to change device addresses, irqs and dma channels is not permitted when the kernel is locked down\n");
+		retval = -EPERM;
+		goto exit;
+	}
+
 	if (!capable(CAP_SYS_ADMIN)) {
 		retval = -EPERM;
 		if (change_irq || change_port ||

From 8620c5939e7e42f1dd4a06221bccb7994ba702cd Mon Sep 17 00:00:00 2001
From: Vito Caputo <vito.caputo@coreos.com>
Date: Wed, 25 Nov 2015 02:59:45 -0800
Subject: [PATCH 23/25] kbuild: derive relative path for KBUILD_SRC from CURDIR

This enables relocating source and build trees to different roots,
provided they stay reachable relative to one another.  Useful for
builds done within a sandbox where the eventual root is prefixed
by some undesirable path component.
---
 Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 159901979dec21..036e19eed4a346 100644
--- a/Makefile
+++ b/Makefile
@@ -142,7 +142,8 @@ $(filter-out _all sub-make $(CURDIR)/Makefile, $(MAKECMDGOALS)) _all: sub-make
 
 # Invoke a second make in the output directory, passing relevant variables
 sub-make:
-	$(Q)$(MAKE) -C $(KBUILD_OUTPUT) KBUILD_SRC=$(CURDIR) \
+	$(Q)$(MAKE) -C $(KBUILD_OUTPUT) \
+	KBUILD_SRC=$(shell realpath --relative-to=$(KBUILD_OUTPUT) $(CURDIR)) \
 	-f $(CURDIR)/Makefile $(filter-out _all sub-make,$(MAKECMDGOALS))
 
 # Leave processing to above invocation of make

From 760811c7d8f73050813d1d8e41cb6a5ef98cb31d Mon Sep 17 00:00:00 2001
From: Geoff Levand <geoff@infradead.org>
Date: Fri, 11 Nov 2016 17:28:52 -0800
Subject: [PATCH 24/25] Add arm64 coreos verity hash

Signed-off-by: Geoff Levand <geoff@infradead.org>
---
 arch/arm64/kernel/efi-header.S | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
index 613fc3000677f7..fdaf86c783329c 100644
--- a/arch/arm64/kernel/efi-header.S
+++ b/arch/arm64/kernel/efi-header.S
@@ -103,6 +103,11 @@ section_table:
 
 	.set	section_count, (. - section_table) / 40
 
+	/* CoreOS 64 byte verity hash value. */
+	.org	_head + 512
+	.ascii	"verity-hash"
+	.org	_head + 512 + 64
+
 #ifdef CONFIG_DEBUG_EFI
 	/*
 	 * The debug table is referenced via its Relative Virtual Address (RVA),

From 8bd2b1562182bc03feed4fc7c6afa3094c0f325b Mon Sep 17 00:00:00 2001
From: Xin Long <lucien.xin@gmail.com>
Date: Sun, 27 Aug 2017 20:25:26 +0800
Subject: [PATCH 25/25] scsi: fix the issue that iscsi_if_rx doesn't parse
 nlmsg properly

ChunYu found a kernel crash by syzkaller:

[  651.617875] kasan: CONFIG_KASAN_INLINE enabled
[  651.618217] kasan: GPF could be caused by NULL-ptr deref or user memory access
[  651.618731] general protection fault: 0000 [#1] SMP KASAN
[  651.621543] CPU: 1 PID: 9539 Comm: scsi Not tainted 4.11.0.cov #32
[  651.621938] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[  651.622309] task: ffff880117780000 task.stack: ffff8800a3188000
[  651.622762] RIP: 0010:skb_release_data+0x26c/0x590
[...]
[  651.627260] Call Trace:
[  651.629156]  skb_release_all+0x4f/0x60
[  651.629450]  consume_skb+0x1a5/0x600
[  651.630705]  netlink_unicast+0x505/0x720
[  651.632345]  netlink_sendmsg+0xab2/0xe70
[  651.633704]  sock_sendmsg+0xcf/0x110
[  651.633942]  ___sys_sendmsg+0x833/0x980
[  651.637117]  __sys_sendmsg+0xf3/0x240
[  651.638820]  SyS_sendmsg+0x32/0x50
[  651.639048]  entry_SYSCALL_64_fastpath+0x1f/0xc2

It's caused by skb_shared_info at the end of sk_buff was overwritten by
ISCSI_KEVENT_IF_ERROR when parsing nlmsg info from skb in iscsi_if_rx.

During the loop if skb->len == nlh->nlmsg_len and both are sizeof(*nlh),
ev = nlmsg_data(nlh) will acutally get skb_shinfo(SKB) instead and set a
new value to skb_shinfo(SKB)->nr_frags by ev->type.

This patch is to fix it by checking nlh->nlmsg_len properly there to
avoid over accessing sk_buff.

Reported-by: ChunYu Wang <chunwang@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Chris Leech <cleech@redhat.com>
---
 drivers/scsi/scsi_transport_iscsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index a424eaeafeb098..c55c6f3147aee5 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -3689,7 +3689,7 @@ iscsi_if_rx(struct sk_buff *skb)
 		uint32_t group;
 
 		nlh = nlmsg_hdr(skb);
-		if (nlh->nlmsg_len < sizeof(*nlh) ||
+		if (nlh->nlmsg_len < sizeof(*nlh) + sizeof(*ev) ||
 		    skb->len < nlh->nlmsg_len) {
 			break;
 		}