Although we do check the completion-status of the request before
actually adding a wait on it (either to its submit fence or its
completion dma-fence), we currently do not check before adding it to the
dependency lists.
In fact, without checking for a completed request we may try to use the
signaler after it has been retired and its dependency tree freed:
[ 60.044057] BUG: KASAN: use-after-free in __list_add_valid+0x1d/0xd0 at addr ffff880348c9e6a0
[ 60.044118] Read of size 8 by task gem_exec_fence/530
[ 60.044164] CPU: 1 PID: 530 Comm: gem_exec_fence Tainted: G E 4.11.0-rc7+ #46
[ 60.044226] Hardware name: ��������������������������������� ���������������������������������/���������������������������������, BIOS RYBDWi35.86A.0246.2
[ 60.044290] Call Trace:
[ 60.044337] dump_stack+0x4d/0x6a
[ 60.044383] kasan_object_err+0x21/0x70
[ 60.044435] kasan_report+0x225/0x4e0
[ 60.044488] ? __list_add_valid+0x1d/0xd0
[ 60.044534] ? kasan_kmalloc+0xad/0xe0
[ 60.044587] __asan_load8+0x5e/0x70
[ 60.044639] __list_add_valid+0x1d/0xd0
[ 60.044788] __i915_priotree_add_dependency+0x67/0x130 [i915]
[ 60.044895] i915_gem_request_await_request+0xa8/0x370 [i915]
[ 60.044974] i915_gem_request_await_dma_fence+0x129/0x140 [i915]
[ 60.045049] i915_gem_do_execbuffer.isra.37+0xb0a/0x26b0 [i915]
[ 60.045077] ? save_stack+0xb1/0xd0
[ 60.045105] ? save_stack_trace+0x1b/0x20
[ 60.045132] ? save_stack+0x46/0xd0
[ 60.045158] ? kasan_kmalloc+0xad/0xe0
[ 60.045184] ? __kmalloc+0xd8/0x670
[ 60.045229] ? drm_ioctl+0x359/0x640 [drm]
[ 60.045256] ? SyS_ioctl+0x41/0x70
[ 60.045330] ? i915_vma_move_to_active+0x540/0x540 [i915]
[ 60.045360] ? tty_insert_flip_string_flags+0xa1/0xf0
[ 60.045387] ? tty_flip_buffer_push+0x63/0x70
[ 60.045414] ? remove_wait_queue+0xa9/0xc0
[ 60.045441] ? kasan_unpoison_shadow+0x35/0x50
[ 60.045467] ? kasan_kmalloc+0xad/0xe0
[ 60.045494] ? kasan_check_write+0x14/0x20
[ 60.045568] i915_gem_execbuffer2+0xdb/0x2a0 [i915]
[ 60.045616] drm_ioctl+0x359/0x640 [drm]
[ 60.045705] ? i915_gem_execbuffer+0x5a0/0x5a0 [i915]
[ 60.045751] ? drm_version+0x150/0x150 [drm]
[ 60.045778] ? compat_start_thread+0x60/0x60
[ 60.045805] ? plist_del+0xda/0x1a0
[ 60.045833] do_vfs_ioctl+0x12e/0x910
[ 60.045860] ? ioctl_preallocate+0x130/0x130
[ 60.045886] ? pci_mmcfg_check_reserved+0xc0/0xc0
[ 60.045913] ? vfs_write+0x196/0x240
[ 60.045939] ? __fget_light+0xa7/0xc0
[ 60.045965] SyS_ioctl+0x41/0x70
[ 60.045991] entry_SYSCALL_64_fastpath+0x17/0x98
[ 60.046017] RIP: 0033:0x7feb2baefc47
[ 60.046042] RSP: 002b:00007fff56d28e58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[ 60.046075] RAX: ffffffffffffffda RBX: 00007fff56d290a8 RCX: 00007feb2baefc47
[ 60.046102] RDX: 00007fff56d29050 RSI: 00000000c0406469 RDI: 0000000000000003
[ 60.046129] RBP: 00007fff56d29050 R08: 000055ecc4cd27d0 R09: 00007feb2bda8600
[ 60.046154] R10: 0000000000000073 R11: 0000000000000246 R12: 00000000c0406469
[ 60.046177] R13: 0000000000000003 R14: 000000000000000f R15: 0000000000000099
[ 60.046203] Object at ffff880348c9e680, in cache i915_dependency size: 64
[ 60.046225] Allocated:
[ 60.046246] PID = 530
[ 60.046269] save_stack_trace+0x1b/0x20
[ 60.046292] save_stack+0x46/0xd0
[ 60.046318] kasan_kmalloc+0xad/0xe0
[ 60.046343] kasan_slab_alloc+0x12/0x20
[ 60.046368] kmem_cache_alloc+0xab/0x650
[ 60.046445] i915_gem_request_await_request+0x88/0x370 [i915]
[ 60.046559] i915_gem_request_await_dma_fence+0x129/0x140 [i915]
[ 60.046705] i915_gem_do_execbuffer.isra.37+0xb0a/0x26b0 [i915]
[ 60.046849] i915_gem_execbuffer2+0xdb/0x2a0 [i915]
[ 60.046936] drm_ioctl+0x359/0x640 [drm]
[ 60.046987] do_vfs_ioctl+0x12e/0x910
[ 60.047038] SyS_ioctl+0x41/0x70
[ 60.047090] entry_SYSCALL_64_fastpath+0x17/0x98
[ 60.047139] Freed:
[ 60.047179] PID = 530
[ 60.047223] save_stack_trace+0x1b/0x20
[ 60.047269] save_stack+0x46/0xd0
[ 60.047317] kasan_slab_free+0x72/0xc0
[ 60.047366] kmem_cache_free+0x39/0x160
[ 60.047512] i915_gem_request_retire+0x83f/0x930 [i915]
[ 60.047657] i915_gem_request_alloc+0x166/0x600 [i915]
[ 60.047799] i915_gem_do_execbuffer.isra.37+0xad8/0x26b0 [i915]
[ 60.047897] i915_gem_execbuffer2+0xdb/0x2a0 [i915]
[ 60.047942] drm_ioctl+0x359/0x640 [drm]
[ 60.047968] do_vfs_ioctl+0x12e/0x910
[ 60.047993] SyS_ioctl+0x41/0x70
[ 60.048019] entry_SYSCALL_64_fastpath+0x17/0x98
[ 60.048044] Memory state around the buggy address:
[ 60.048066] ffff880348c9e580: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 60.048105] ffff880348c9e600: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 60.048138] >ffff880348c9e680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
[ 60.048170] ^
[ 60.048191] ffff880348c9e700: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
[ 60.048225] ffff880348c9e780: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
Note to hit the use-after-free requires us to be passed back a request
via a fence-array, that is from explicit fencing accumulated into a
sync-file fence-array.
Fixes: 52e542090701 ("drm/i915/scheduler: Record all dependencies upon request construction")
Testcase: igt/gem_exec_fence/expired-history
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_request.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 095cccc2e8b2..e2ec42b2bf24 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -680,6 +680,9 @@ i915_gem_request_await_request(struct drm_i915_gem_request *to,
GEM_BUG_ON(to == from);
+ if (i915_gem_request_completed(from))
+ return 0;
+
if (to->engine->schedule) {
ret = i915_priotree_add_dependency(to->i915,
&to->priotree,
--
2.11.0
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