Error building evdi on Fedora 39 / Linux 6.7.9

[Tahaan]

• Are you using the latest driver?

Installed Packages
Name         : displaylink
Version      : 1.14.1
Release      : 2

• Are you using the latest EVDI version?

johan@fedora ~/evdi (main)> git remote -v
origin  https://github.com/DisplayLink/evdi (fetch)
origin  https://github.com/DisplayLink/evdi (push)
johan@fedora ~/evdi (main)> git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean
johan@fedora ~/evdi (main)> git log -1
commit 9905b9bfed8b7e49befa0530bfb6e464380d938f (HEAD -> main, tag: v1.14.2, origin/main, origin/HEAD)
Author: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
Date:   Wed Jan 31 11:30:22 2024 +0100

    Set version to 1.14.2
johan@fedora ~/evdi (main)> 

• If you are using a DisplayLink device, have you checked 'troubleshooting'
  on DisplayLink's website?

The same device works fine with either Windows and with KDE-Neon using the Ubuntu packages from the Synaptic web site.

• Is this issue related to evdi/kernel?

Building evdi

• Linux distribution and its version

johan@fedora ~/evdi (main)> uname -a
Linux fedora 6.7.9-200.fc39.x86_64 #1 SMP PREEMPT_DYNAMIC Wed Mar  6 19:35:04 UTC 2024 x86_64 GNU/Linux

• Linux kernel version
  6.7.9-200.fc39.x86_64

• Xorg version (if used)
  Plasma 5.27.11, kwin, Not really relevant.

• Desktop environment in use
  KDE/Plasma, not really relevant.

I am hoping that building a newer version of evdi will solve the issue, as I dont know what else to look at. (The problem I am trying to solve is best described by watching this video: https://youtu.be/uZeN9UesBUY)

The error below occurs when trying to build.

johan@fedora ~/evdi (main)> make 
CFLAGS="-isystem./include -isystem./include/uapi -Werror -Wextra -Wall -Wno-error=missing-field-initializers -Werror=sign-compare -Wmissing-prototypes -Wstrict-prototypes -Werror=discarded-qualifiers " make -C module 
make[1]: Entering directory '/home/johan/evdi/module'
make -C /lib/modules/6.7.9-200.fc39.x86_64/build M=$PWD
make[2]: Entering directory '/usr/src/kernels/6.7.9-200.fc39.x86_64'
warning: the compiler differs from the one used to build the kernel
  The kernel was built by: gcc (GCC) 13.2.1 20231205 (Red Hat 13.2.1-6)
  You are using:           gcc (GCC) 13.2.1 20240316 (Red Hat 13.2.1-7)
  CC [M]  /home/johan/evdi/module/evdi_platform_drv.o
  CC [M]  /home/johan/evdi/module/evdi_platform_dev.o
  CC [M]  /home/johan/evdi/module/evdi_sysfs.o
  CC [M]  /home/johan/evdi/module/evdi_modeset.o
  CC [M]  /home/johan/evdi/module/evdi_connector.o
  CC [M]  /home/johan/evdi/module/evdi_encoder.o
  CC [M]  /home/johan/evdi/module/evdi_drm_drv.o
  CC [M]  /home/johan/evdi/module/evdi_fb.o
  CC [M]  /home/johan/evdi/module/evdi_gem.o
/home/johan/evdi/module/evdi_gem.c: In function ‘evdi_gem_fault’:
/home/johan/evdi/module/evdi_gem.c:214:40: error: comparison of integer expressions of different signedness: ‘long unsigned int’ and ‘loff_t’ {aka ‘long long int’} [-Werror=sign-compare]
  214 |         if (!obj->pages || page_offset >= num_pages)
      |                                        ^~
cc1: all warnings being treated as errors
make[4]: *** [scripts/Makefile.build:243: /home/johan/evdi/module/evdi_gem.o] Error 1
make[3]: *** [/usr/src/kernels/6.7.9-200.fc39.x86_64/Makefile:1929: /home/johan/evdi/module] Error 2
make[2]: *** [Makefile:246: __sub-make] Error 2
make[2]: Leaving directory '/usr/src/kernels/6.7.9-200.fc39.x86_64'
make[1]: *** [Makefile:86: module] Error 2
make[1]: Leaving directory '/home/johan/evdi/module'
make: *** [Makefile:13: module] Error 2

[Tahaan]

The below commit seem to be to blame

johan@fedora ~/e/module (main) [128]> git log -p evdi_gem.c 
commit 294af3d4ec5b22012174a3b26b773f939dad7dbd
Author: Łukasz Spintzyk <lukasz.spintzyk@synaptics.com>
Date:   Wed Sep 6 07:49:36 2023 +0200

    Fix possible OOB in evdi_gem_fault

diff --git a/module/evdi_gem.c b/module/evdi_gem.c
index 499d065..efae6e1 100644
--- a/module/evdi_gem.c
+++ b/module/evdi_gem.c
@@ -205,12 +205,13 @@ int evdi_gem_fault(struct vm_fault *vmf)
 #endif
        struct evdi_gem_object *obj = to_evdi_bo(vma->vm_private_data);
        struct page *page;
-       unsigned int page_offset;
+       pgoff_t page_offset;
+       loff_t num_pages = obj->base.size >> PAGE_SHIFT;
        int ret = 0;
 
        page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;
 
-       if (!obj->pages)
+       if (!obj->pages || page_offset >= num_pages)
                return VM_FAULT_SIGBUS;
 
        page = obj->pages[page_offset];

[tanj]

I also ran into this. I'm not sure if this is the right way to handle this, but I worked around it with the following. I cast, what I think is the smaller type of pgoff_t (long unsigned int) to the larger signed loff_t (long long int)

diff --git a/module/evdi_gem.c b/module/evdi_gem.c
index efae6e1..46dc5fa 100644
--- a/module/evdi_gem.c
+++ b/module/evdi_gem.c
@@ -211,7 +211,7 @@ int evdi_gem_fault(struct vm_fault *vmf)

        page_offset = (vmf->address - vma->vm_start) >> PAGE_SHIFT;

-       if (!obj->pages || page_offset >= num_pages)
+       if (!obj->pages || (loff_t)page_offset >= num_pages)
                return VM_FAULT_SIGBUS;

        page = obj->pages[page_offset];

[arnigb]

@tanj the same Issue still occurs on Pop_OS! (kernel 6.8.0)

/my/directory/path/evdi/module/evdi_gem.c: In function ‘evdi_gem_fault’:
/my/directory/path/evdi/module/evdi_gem.c:214:40: error: comparison of integer expressions of different signedness: ‘long unsigned int’ and ‘loff_t’ {aka ‘long long int’} [-Werror=sign-compare]
214 | if (!obj->pages || page_offset >= num_pages)
| ^~
cc1: all warnings being treated as errors
make[4]: *** [scripts/Makefile.build:243: /my/directory/path/evdi/module/evdi_gem.o] Error 1
make[3]: *** [/usr/src/linux-headers-6.8.0-76060800daily20240311-generic/Makefile:1927: /my/directory/path/evdi/module] Error 2
make[2]: *** [Makefile:240: __sub-make] Error 2
make[2]: Leaving directory '/usr/src/linux-headers-6.8.0-76060800daily20240311-generic'
make[1]: *** [Makefile:86: module] Error 2
make[1]: Leaving directory '/my/directory/path/evdi/module'
make: *** [Makefile:13: module] Error 2

[displaylink-emajewsk]

Fixed in 1.14.3