Medium · published May 1, 2024
In the Linux kernel, the following vulnerability has been resolved:
drm/vmwgfx: Create debugfs ttm_resource_manager entry only if needed
The driver creates /sys/kernel/debug/dri/0/mob_ttm even when the
corresponding ttm_resource_manager is not allocated.
This leads to a crash when trying to read from this file.
Add a check to create mob_ttm, system_mob_ttm, and gmr_ttm debug file
only when the corresponding ttm_resource_manager is allocated.
crash> bt
PID: 3133409 TASK: ffff8fe4834a5000 CPU: 3 COMMAND: "grep"
#0 [ffffb954506b3b20] machine_kexec at ffffffffb2a6bec3
#1 [ffffb954506b3b78] __crash_kexec at ffffffffb2bb598a
#2 [ffffb954506b3c38] crash_kexec at ffffffffb2bb68c1
#3 [ffffb954506b3c50] oops_end at ffffffffb2a2a9b1
#4 [ffffb954506b3c70] no_context at ffffffffb2a7e913
#5 [ffffb954506b3cc8] __bad_area_nosemaphore at ffffffffb2a7ec8c
#6 [ffffb954506b3d10] do_page_fault at ffffffffb2a7f887
#7 [ffffb954506b3d40] page_fault at ffffffffb360116e
[exception RIP: ttm_resource_manager_debug+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
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#8 [ffffb954506b3e00] ttm_resource_manager_show at ffffffffc04afde7 [ttm]
#9 [ffffb954506b3e30] seq_read 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