[Intel-gfx] [PATCH 2/3] drm/i915: Pass the right flags to i915_vma_move_to_active()
Chris Wilson
chris at chris-wilson.co.uk
Tue Jun 20 20:15:21 UTC 2017
Quoting Tvrtko Ursulin (2017-06-20 16:47:06)
>
> On 20/06/2017 13:43, Chris Wilson wrote:
> > i915_vma_move_to_active() takes the execobject flags and not a boolean!
> > Instead of passing EXEC_OBJECT_WRITE we passed true [i.e.
> > EXEC_OBJECT_NEEDS_FENCE] causing us to start tracking the
> > vma->last_fence access and since we forgot to clear that on unbinding,
> > we caused a use-after-free.
> >
> > [ 321.263854] BUG: KASAN: use-after-free in i915_gem_request_retire+0x1728/0x1740 [i915]
> > [ 321.264001] Read of size 8 at addr ffff880100fc67d8 by task gem_exec_reloc/2868
> >
> > [ 321.264181] CPU: 0 PID: 2868 Comm: gem_exec_reloc Not tainted 4.12.0-rc6-CI-Custom_2759+ #1
> > [ 321.264195] Hardware name: GIGABYTE GB-BXBT-1900/MZBAYAB-00, BIOS F6 02/17/2015
> > [ 321.264208] Call Trace:
> > [ 321.264234] dump_stack+0x67/0x99
> > [ 321.264260] print_address_description+0x77/0x290
> > [ 321.264437] ? i915_gem_request_retire+0x1728/0x1740 [i915]
> > [ 321.264459] kasan_report+0x269/0x350
> > [ 321.264487] __asan_report_load8_noabort+0x14/0x20
> > [ 321.264660] i915_gem_request_retire+0x1728/0x1740 [i915]
> > [ 321.264841] ? intel_ring_context_pin+0x131/0x690 [i915]
> > [ 321.265021] i915_gem_request_alloc+0x2c6/0x1220 [i915]
> > [ 321.265044] ? _raw_spin_unlock_irqrestore+0x3d/0x60
> > [ 321.265226] i915_gem_do_execbuffer+0xac0/0x2a20 [i915]
> > [ 321.265250] ? __lock_acquire+0xceb/0x5450
> > [ 321.265269] ? entry_SYSCALL_64_fastpath+0x1c/0xb1
> > [ 321.265291] ? kvmalloc_node+0x6b/0x80
> > [ 321.265310] ? kvmalloc_node+0x6b/0x80
> > [ 321.265489] ? eb_relocate_slow+0xbe0/0xbe0 [i915]
> > [ 321.265520] ? ___slab_alloc.constprop.28+0x2ab/0x3d0
> > [ 321.265549] ? debug_check_no_locks_freed+0x280/0x280
> > [ 321.265591] ? __might_fault+0xc6/0x1b0
> > [ 321.265782] i915_gem_execbuffer2+0x14a/0x3f0 [i915]
> > [ 321.265815] drm_ioctl+0x4ba/0xaa0
> > [ 321.265986] ? i915_gem_execbuffer+0xde0/0xde0 [i915]
> > [ 321.266017] ? drm_getunique+0x270/0x270
> > [ 321.266068] do_vfs_ioctl+0x17f/0xfa0
> > [ 321.266091] ? __fget+0x1ba/0x330
> > [ 321.266112] ? lock_acquire+0x390/0x390
> > [ 321.266133] ? ioctl_preallocate+0x1d0/0x1d0
> > [ 321.266164] ? __fget+0x1db/0x330
> > [ 321.266194] ? __fget_light+0x79/0x1f0
> > [ 321.266219] SyS_ioctl+0x3c/0x70
> > [ 321.266247] entry_SYSCALL_64_fastpath+0x1c/0xb1
> > [ 321.266265] RIP: 0033:0x7fcede207357
> > [ 321.266279] RSP: 002b:00007ffef0effe58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > [ 321.266307] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fcede207357
> > [ 321.266321] RDX: 00007ffef0effef0 RSI: 0000000040406469 RDI: 0000000000000004
> > [ 321.266335] RBP: ffffffff812097c6 R08: 0000000000000008 R09: 0000000000000000
> > [ 321.266349] R10: 0000000000000008 R11: 0000000000000246 R12: ffff880116bcff98
> > [ 321.266363] R13: ffffffff81cb7cb3 R14: ffff880116bcff70 R15: 0000000000000000
> > [ 321.266385] ? __this_cpu_preempt_check+0x13/0x20
> > [ 321.266406] ? trace_hardirqs_off_caller+0x1d6/0x2c0
> >
> > [ 321.266487] Allocated by task 2868:
> > [ 321.266568] save_stack_trace+0x16/0x20
> > [ 321.266586] kasan_kmalloc+0xee/0x180
> > [ 321.266602] kasan_slab_alloc+0x12/0x20
> > [ 321.266620] kmem_cache_alloc+0xc7/0x2e0
> > [ 321.266795] i915_vma_instance+0x28c/0x1540 [i915]
> > [ 321.266964] eb_lookup_vmas+0x5a7/0x2250 [i915]
> > [ 321.267130] i915_gem_do_execbuffer+0x69a/0x2a20 [i915]
> > [ 321.267296] i915_gem_execbuffer2+0x14a/0x3f0 [i915]
> > [ 321.267315] drm_ioctl+0x4ba/0xaa0
> > [ 321.267333] do_vfs_ioctl+0x17f/0xfa0
> > [ 321.267350] SyS_ioctl+0x3c/0x70
> > [ 321.267369] entry_SYSCALL_64_fastpath+0x1c/0xb1
> >
> > [ 321.267428] Freed by task 177:
> > [ 321.267502] save_stack_trace+0x16/0x20
> > [ 321.267521] kasan_slab_free+0xad/0x180
> > [ 321.267539] kmem_cache_free+0xc5/0x340
> > [ 321.267710] i915_vma_unbind+0x666/0x10a0 [i915]
> > [ 321.267880] i915_vma_close+0x23a/0x2f0 [i915]
> > [ 321.268048] __i915_gem_free_objects+0x17d/0xc70 [i915]
> > [ 321.268215] __i915_gem_free_work+0x49/0x70 [i915]
> > [ 321.268234] process_one_work+0x66f/0x1410
> > [ 321.268252] worker_thread+0xe1/0xe90
> > [ 321.268269] kthread+0x304/0x410
> > [ 321.268285] ret_from_fork+0x27/0x40
> >
> > [ 321.268346] The buggy address belongs to the object at ffff880100fc6640
> > which belongs to the cache i915_vma of size 656
> > [ 321.268550] The buggy address is located 408 bytes inside of
> > 656-byte region [ffff880100fc6640, ffff880100fc68d0)
> > [ 321.268741] The buggy address belongs to the page:
> > [ 321.268837] page:ffffea000403f000 count:1 mapcount:0 mapping: (null) index:0xffff880100fc5980 compound_mapcount: 0
> > [ 321.269045] flags: 0x8000000000008100(slab|head)
> > [ 321.269147] raw: 8000000000008100 0000000000000000 ffff880100fc5980 00000001001e001d
> > [ 321.269312] raw: ffffea0004038e20 ffff880116b46240 ffff88011646c640 0000000000000000
> > [ 321.269484] page dumped because: kasan: bad access detected
> >
> > [ 321.269665] Memory state around the buggy address:
> > [ 321.269778] ffff880100fc6680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 321.269949] ffff880100fc6700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 321.270115] >ffff880100fc6780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 321.270279] ^
> > [ 321.270410] ffff880100fc6800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [ 321.270576] ffff880100fc6880: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
> > [ 321.270740] ==================================================================
> > [ 321.270903] Disabling lock debugging due to kernel taint
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101511
> > Fixes: 7dd4f6729f92 ("drm/i915: Async GPU relocation processing")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/i915_gem_execbuffer.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index eb46dfa374a7..a23a1c3503c8 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -1199,7 +1199,7 @@ static int __reloc_gpu_alloc(struct i915_execbuffer *eb,
> > reservation_object_unlock(batch->resv);
> > i915_vma_unpin(batch);
> >
> > - i915_vma_move_to_active(vma, rq, true);
> > + i915_vma_move_to_active(vma, rq, EXEC_OBJECT_WRITE);
> > reservation_object_lock(vma->resv, NULL);
> > reservation_object_add_excl_fence(vma->resv, &rq->fence);
> > reservation_object_unlock(vma->resv);
> >
>
> This one is straightforward.
>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Thanks for the review, pushed the fix for the brainfart. Will come back
to the older issue in the morning if I've managed to clarify the logic.
-Chris
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