[Bug 219007] New: opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[Bug 219007] New: opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

            Bug ID: 219007
           Summary: opening and closing /dev/dri/card0 in a QEMU KVM
                    instance will shutdown system, 6.10.0-rc6+
           Product: Drivers
           Version: 2.5
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Video(DRI - non Intel)
          Assignee: drivers_video-dri@kernel-bugs.osdl.org
          Reporter: colin.i.king@gmail.com
        Regression: No

The following code when run as root on a Debian sid amd64 server running in
virt-manager (KVM QEMU) will shut the system down with 6.10.0-rc6.  The fork()
is required to cause racing on the open/close on /dev/dri/card0

#include <fcntl.h>
#include <unistd.h>

int main(void)
{
         pid_t pid = fork();

         while (1) {
                int fd;

                fd = openat(AT_FDCWD, "/dev/dri/card0",
O_WRONLY|O_NONBLOCK|O_SYNC);
                close(fd);
         }
}

This was originally found using: while true; do sudo ./stress-ng  --dev 4
--dev-file /dev/dri/card0 -t 5; done and narrowed down to the above reproducer.
(cf: https://github.com/ColinIanKing/stress-ng/issues/407 )

This does not occur on pre 6.10 kernels, so it looks like a 6.10 regression.

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

Colin Ian King (colin.i.king@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|All                         |Intel
           Severity|normal                      |high

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

--- Comment #1 from Colin Ian King (colin.i.king@gmail.com) ---
Note this also can reproduce when running *without* root privileged too, so
this is a user space DoS attack vector.

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

The Linux kernel's regression tracker (Thorsten Leemhuis) (regressions@leemhuis.info) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |regressions@leemhuis.info

--- Comment #2 from The Linux kernel's regression tracker (Thorsten Leemhuis) (regressions@leemhuis.info) ---
Colin, quick reminder: many bugs reported here are never forwarded to any
developer. For some of the details see https://lwn.net/Articles/910740/ and the
links in there. So the people you are trying to reach most likely won't even
see this.

Mail is usually the best for reporting, as mentioned in
https://docs.kernel.org/admin-guide/reporting-issues.html (which also tells
people to avoid bugzilla in most cases)

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

--- Comment #3 from The Linux kernel's regression tracker (Thorsten Leemhuis) (regressions@leemhuis.info) ---
Forgot: I'll forward this report by mail, as it's a regression, so no need to
do anything for you. But it's not the first bug I see from you here, so I
thought a reminder might be wise.

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

--- Comment #4 from The Linux kernel's regression tracker (Thorsten Leemhuis) (regressions@leemhuis.info) ---
And one more comment: could you please share a dmesg from the VM so we know
what drm driver is used.

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[Bug 219007] opening and closing /dev/dri/card0 in a QEMU KVM instance will shutdown system, 6.10.0-rc6+

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=219007

Colin Ian King (colin.i.king@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |colin.i.king@gmail.com

--- Comment #5 from Colin Ian King (colin.i.king@gmail.com) ---
Created attachment 306610
  --> https://bugzilla.kernel.org/attachment.cgi?id=306610&action=edit
dmesg 6.10 log

Attached, dmesg log. Apologies for the delayed reply.

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