In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/i915: Fix potential UAF in TTM object purge<\/p>\n
TLDR: The bo->ttm object might be changed by calling ttm_bo_validate(),
\n move casting it to an i915_tt object later to actually get the right
\n pointer.<\/p>\n
A user reported hitting the following bug under heavy use on DG2:<\/p>\n
[26620.095550] Oops: general protection fault, probably for non-canonical address 0xa56b6b6b6b6b6b8b: 0000 1 SMP NOPTI
\n[26620.095556] CPU: 2 UID: 0 PID: 631 Comm: Xorg Not tainted 6.18.8 #1 PREEMPT(lazy)
\n[26620.095558] Hardware name: ASRock B850M Steel Legend WiFi\/B850M Steel Legend WiFi, BIOS 3.50 09\/18\/2025
\n[26620.095559] RIP: 0010:i915_ttm_purge+0x84\/0x100 [i915]
\n[26620.095604] Code: 00 00 00 48 8d 54 24 10 48 89 e6 48 89 fb e8 83 aa ae ff 85 c0 75 6f 48 83 bb a8 01 00 00 00 74 2c 48 8b 45 78 48 85 c0 74 23 8b 78 20 48 c7 c2 ff ff ff ff 31 f6 e8 7a 73 e3 e0 48 8b 7d 78
\n[26620.095605] RSP: 0018:ffffc90005fd7430 EFLAGS: 00010282
\n[26620.095607] RAX: a56b6b6b6b6b6b6b RBX: ffff8881f46c3dc0 RCX: 0000000000000000
\n[26620.095608] RDX: 0000000000000000 RSI: 0000000000000246 RDI: 00000000ffffffff
\n[26620.095609] RBP: ffff888289610f00 R08: 0000000000000001 R09: ffff88823b022000
\n[26620.095609] R10: ffff888103029b28 R11: ffff8881fc7f3800 R12: ffff88810b6150d0
\n[26620.095609] R13: ffff888289610f00 R14: 0000000000000000 R15: ffff8881f46c3dc0
\n[26620.095610] FS: 00007f1004d86900(0000) GS:ffff88901c858000(0000) knlGS:0000000000000000
\n[26620.095611] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
\n[26620.095611] CR2: 00007f0fdf489000 CR3: 000000035b0c1000 CR4: 0000000000750ef0
\n[26620.095612] PKRU: 55555554
\n[26620.095612] Call Trace:
\n[26620.095615]
\n[26620.095615] i915_ttm_move+0x2b9\/0x420 [i915]
\n[26620.095642] ? ttm_tt_init+0x65\/0x80 [ttm]
\n[26620.095644] ? i915_ttm_tt_create+0xc6\/0x150 [i915]
\n[26620.095667] ttm_bo_handle_move_mem+0xb6\/0x160 [ttm]
\n[26620.095669] ttm_bo_evict+0x100\/0x150 [ttm]
\n[26620.095671] ? preempt_count_add+0x64\/0xa0
\n[26620.095673] ? _raw_spin_lock+0xe\/0x30
\n[26620.095675] ? _raw_spin_unlock+0xd\/0x30
\n[26620.095675] ? i915_gem_object_evictable+0xb7\/0xd0 [i915]
\n[26620.095704] ttm_bo_evict_cb+0x6e\/0xd0 [ttm]
\n[26620.095705] ttm_lru_walk_for_evict+0xa6\/0x200 [ttm]
\n[26620.095708] ttm_bo_alloc_resource+0x185\/0x4f0 [ttm]
\n[26620.095709] ? init_object+0x62\/0xd0
\n[26620.095712] ttm_bo_validate+0x7a\/0x180 [ttm]
\n[26620.095713] ? _raw_spin_unlock_irqrestore+0x16\/0x30
\n[26620.095714] __i915_ttm_get_pages+0xb0\/0x170 [i915]
\n[26620.095737] i915_ttm_get_pages+0x9f\/0x150 [i915]
\n[26620.095759] ? i915_gem_do_execbuffer+0xedc\/0x2b40 [i915]
\n[26620.095786] ? alloc_debug_processing+0xd0\/0x100
\n[26620.095787] ? _raw_spin_unlock_irqrestore+0x16\/0x30
\n[26620.095788] ? i915_vma_instance+0xa0\/0x4e0 [i915]
\n[26620.095822] __i915_gem_object_get_pages+0x2f\/0x40 [i915]
\n[26620.095848] i915_vma_pin_ww+0x706\/0x980 [i915]
\n[26620.095875] ? i915_gem_do_execbuffer+0xedc\/0x2b40 [i915]
\n[26620.095904] eb_validate_vmas+0x170\/0xa00 [i915]
\n[26620.095930] i915_gem_do_execbuffer+0x1201\/0x2b40 [i915]
\n[26620.095953] ? alloc_debug_processing+0xd0\/0x100
\n[26620.095954] ? _raw_spin_unlock_irqrestore+0x16\/0x30
\n[26620.095955] ? i915_gem_execbuffer2_ioctl+0xc9\/0x240 [i915]
\n[26620.095977] ? __wake_up_sync_key+0x32\/0x50
\n[26620.095979] ? i915_gem_execbuffer2_ioctl+0xc9\/0x240 [i915]
\n[26620.096001] ? __slab_alloc.isra.0+0x67\/0xc0
\n[26620.096003] i915_gem_execbuffer2_ioctl+0x11a\/0x240 [i915]<\/p>\n
Results from decode_stacktrace.sh pointed to dereference of a file pointer
\nfield of a i915 TTM page vector container associated with an object being
\npurged on eviction. That path is taken when the object is marked as no
\nlonger needed.<\/p>\n
Code analysis revealed a possibility of the i915 TTM page vector container
\nbeing replaced with a new instance inside a function that purges content
\nof the object, should it be still busy. That function is called,
\nindirectly via a more general function that changes the object’s placement
\nand caching policy,
\n—truncated—<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/i915: Fix potential UAF in TTM object purge<\/p>\n
TLDR: The bo->ttm object might be changed by calling ttm_bo_validate(),
\n move<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-14938","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/14938","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14938"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14938"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14938"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}