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Fix userfaultfd_api to return EINVAL as expected
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commit 1723f04 upstream.

Currently if we request a feature that is not set in the Kernel config we
fail silently and return all the available features.  However, the man
page indicates we should return an EINVAL.

We need to fix this issue since we can end up with a Kernel warning should
a program request the feature UFFD_FEATURE_WP_UNPOPULATED on a kernel with
the config not set with this feature.

 [  200.812896] WARNING: CPU: 91 PID: 13634 at mm/memory.c:1660 zap_pte_range+0x43d/0x660
 [  200.820738] Modules linked in:
 [  200.869387] CPU: 91 PID: 13634 Comm: userfaultfd Kdump: loaded Not tainted 6.9.0-rc5+ Freescale#8
 [  200.877477] Hardware name: Dell Inc. PowerEdge R6525/0N7YGH, BIOS 2.7.3 03/30/2022
 [  200.885052] RIP: 0010:zap_pte_range+0x43d/0x660

Link: https://lkml.kernel.org/r/20240626130513.120193-1-audra@redhat.com
Fixes: e06f1e1 ("userfaultfd: wp: enabled write protection in userfaultfd API")
Signed-off-by: Audra Mitchell <audra@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Audra Mitchell authored and Florian Bezannier committed Aug 23, 2024
1 parent 0f6237e commit d51aaed
Showing 1 changed file with 6 additions and 1 deletion.
7 changes: 6 additions & 1 deletion fs/userfaultfd.c
Original file line number Diff line number Diff line change
@@ -1935,7 +1935,7 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
goto out;
features = uffdio_api.features;
ret = -EINVAL;
if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES))
if (uffdio_api.api != UFFD_API)
goto err_out;
ret = -EPERM;
if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE))
@@ -1949,6 +1949,11 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
#endif

ret = -EINVAL;
if (features & ~uffdio_api.features)
goto err_out;

uffdio_api.ioctls = UFFD_API_IOCTLS;
ret = -EFAULT;
if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))

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