CVE-2024-26940

In the Linux kernel, the following vulnerability has been resolved:

drm/vmwgfx: Create debugfs ttmresourcemanager entry only if needed

The driver creates /sys/kernel/debug/dri/0/mobttm even when the corresponding ttmresource_manager is not allocated. This leads to a crash when trying to read from this file.

Add a check to create mobttm, systemmobttm, and gmrttm debug file only when the corresponding ttmresourcemanager is allocated.

crash> bt PID: 3133409 TASK: ffff8fe4834a5000 CPU: 3 COMMAND: "grep" #0 [ffffb954506b3b20] machinekexec at ffffffffb2a6bec3 #1 [ffffb954506b3b78] _crashkexec at ffffffffb2bb598a #2 [ffffb954506b3c38] crashkexec at ffffffffb2bb68c1 #3 [ffffb954506b3c50] oopsend at ffffffffb2a2a9b1 #4 [ffffb954506b3c70] nocontext at ffffffffb2a7e913 #5 [ffffb954506b3cc8] _badareanosemaphore at ffffffffb2a7ec8c #6 [ffffb954506b3d10] dopagefault at ffffffffb2a7f887 #7 [ffffb954506b3d40] pagefault at ffffffffb360116e [exception RIP: ttmresourcemanagerdebug+0x11] RIP: ffffffffc04afd11 RSP: ffffb954506b3df0 RFLAGS: 00010246 RAX: ffff8fe41a6d1200 RBX: 0000000000000000 RCX: 0000000000000940 RDX: 0000000000000000 RSI: ffffffffc04b4338 RDI: 0000000000000000 RBP: ffffb954506b3e08 R8: ffff8fee3ffad000 R9: 0000000000000000 R10: ffff8fe41a76a000 R11: 0000000000000001 R12: 00000000ffffffff R13: 0000000000000001 R14: ffff8fe5bb6f3900 R15: ffff8fe41a6d1200 ORIGRAX: ffffffffffffffff CS: 0010 SS: 0018 #8 [ffffb954506b3e00] ttmresourcemanagershow at ffffffffc04afde7 [ttm] #9 [ffffb954506b3e30] seqread at ffffffffb2d8f9f3 RIP: 00007f4c4eda8985 RSP: 00007ffdbba9e9f8 RFLAGS: 00000246 RAX: ffffffffffffffda RBX: 000000000037e000 RCX: 00007f4c4eda8985 RDX: 000000000037e000 RSI: 00007f4c41573000 RDI: 0000000000000003 RBP: 000000000037e000 R8: 0000000000000000 R9: 000000000037fe30 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4c41573000 R13: 0000000000000003 R14: 00007f4c41572010 R15: 0000000000000003 ORIG_RAX: 0000000000000000 CS: 0033 SS: 002b