Quoting Chris Wilson (2018-10-25 21:20:21) > Quoting Chris Wilson (2018-10-25 21:15:17) > > Quoting Christian König (2018-10-04 14:12:43) > > > No need for that any more. Just replace the list when there isn't enough > > > room any more for the additional fence. > > > > Just a heads up. After this series landed, we started hitting a > > use-after-free when iterating the shared list. > > > > <4> [109.613162] general protection fault: 0000 [#1] PREEMPT SMP PTI > > <4> [109.613177] CPU: 1 PID: 1357 Comm: gem_busy Tainted: G U 4.19.0-rc8-CI-CI_DRM_5035+ #1 > > <4> [109.613189] Hardware name: Dell Inc. XPS 8300 /0Y2MRG, BIOS A06 10/17/2011 > > <4> [109.613252] RIP: 0010:i915_gem_busy_ioctl+0x146/0x380 [i915] > > <4> [109.613261] Code: 0b 43 04 49 83 c6 08 4d 39 e6 89 43 04 74 6d 4d 8b 3e e8 5d 54 f4 e0 85 c0 74 0d 80 3d 08 71 1d 00 00 0f 84 bb 00 00 00 31 c0 <49> 81 7f 08 20 3a 2c a0 75 cc 41 8b 97 50 02 00 00 49 8b 8f a8 00 > > <4> [109.613283] RSP: 0018:ffffc9000044bcf8 EFLAGS: 00010246 > > <4> [109.613292] RAX: 0000000000000000 RBX: ffffc9000044bdc0 RCX: 0000000000000001 > > <4> [109.613302] RDX: 0000000000000000 RSI: 00000000ffffffff RDI: ffffffff822474a0 > > <4> [109.613311] RBP: ffffc9000044bd28 R08: ffff88021e158680 R09: 0000000000000001 > > <4> [109.613321] R10: 0000000000000040 R11: 0000000000000000 R12: ffff88021e1641b8 > > <4> [109.613331] R13: 0000000000000003 R14: ffff88021e1641b0 R15: 6b6b6b6b6b6b6b6b > > <4> [109.613341] FS: 00007f9c9fc84980(0000) GS:ffff880227a40000(0000) knlGS:0000000000000000 > > <4> [109.613352] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > <4> [109.613360] CR2: 00007f9c9fcb8000 CR3: 00000002247d4005 CR4: 00000000000606e0 > > First guess would be > > diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c > index 5fb4fd461908..833698a0d548 100644 > --- a/drivers/dma-buf/reservation.c > +++ b/drivers/dma-buf/reservation.c > @@ -169,7 +169,6 @@ void reservation_object_add_shared_fence(struct reservation_object *obj, > } > > BUG_ON(fobj->shared_count >= fobj->shared_max); > - fobj->shared_count++; > > replace: > /* > @@ -177,6 +176,8 @@ void reservation_object_add_shared_fence(struct reservation_object *obj, > * fobj->shared_count is protected by this lock too > */ > RCU_INIT_POINTER(fobj->shared[i], fence); > + if (i == fobj->shared_count) > + fobj->shared_count++; > write_seqcount_end(&obj->seq); > preempt_enable(); > } > > Strictly, perhaps WRITE_ONCE(fobj->shared_count, i + 1); ? Updating shared_count after setting the fence does the trick. -Chris _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
