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linux/drivers/dma-buf
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Tvrtko Ursulin 5e51cc0005 dma-resv: Fix dma_resv_get_fences and dma_resv_copy_fences after conversion 
Cache the count of shared fences in the iterator to avoid dereferencing
the dma_resv_object outside the RCU protection. Otherwise iterator and its
users can observe an incosistent state which makes it impossible to use
safely. Such as:

<6> [187.517041] [IGT] gem_sync: executing
<7> [187.536343] i915 0000:00:02.0: [drm:i915_gem_context_create_ioctl [i915]] HW context 1 created
<7> [187.536793] i915 0000:00:02.0: [drm:i915_gem_context_create_ioctl [i915]] HW context 1 created
<6> [187.551235] [IGT] gem_sync: starting subtest basic-many-each
<1> [188.935462] BUG: kernel NULL pointer dereference, address: 0000000000000010
<1> [188.935485] #PF: supervisor write access in kernel mode
<1> [188.935495] #PF: error_code(0x0002) - not-present page
<6> [188.935504] PGD 0 P4D 0
<4> [188.935512] Oops: 0002 [#1] PREEMPT SMP NOPTI
<4> [188.935521] CPU: 2 PID: 1467 Comm: gem_sync Not tainted 5.15.0-rc4-CI-Patchwork_21264+ #1
<4> [188.935535] Hardware name:  /NUC6CAYB, BIOS AYAPLCEL.86A.0049.2018.0508.1356 05/08/2018
<4> [188.935546] RIP: 0010:dma_resv_get_fences+0x116/0x2d0
<4> [188.935560] Code: 10 85 c0 7f c9 be 03 00 00 00 e8 15 8b df ff eb bd e8 8e c6 ff ff eb b6 41 8b 04 24 49 8b 55 00 48 89 e7 8d 48 01 41 89 0c 24 <4c> 89 34 c2 e8 41 f2 ff ff 49 89 c6 48 85 c0 75 8c 48 8b 44 24 10
<4> [188.935583] RSP: 0018:ffffc900011dbcc8 EFLAGS: 00010202
<4> [188.935593] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: 0000000000000001
<4> [188.935603] RDX: 0000000000000010 RSI: ffffffff822e343c RDI: ffffc900011dbcc8
<4> [188.935613] RBP: ffffc900011dbd48 R08: ffff88812d255bb8 R09: 00000000fffffffe
<4> [188.935623] R10: 0000000000000001 R11: 0000000000000000 R12: ffffc900011dbd44
<4> [188.935633] R13: ffffc900011dbd50 R14: ffff888113d29cc0 R15: 0000000000000000
<4> [188.935643] FS:  00007f68d17e9700(0000) GS:ffff888277900000(0000) knlGS:0000000000000000
<4> [188.935655] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4> [188.935665] CR2: 0000000000000010 CR3: 000000012d0a4000 CR4: 00000000003506e0
<4> [188.935676] Call Trace:
<4> [188.935685]  i915_gem_object_wait+0x1ff/0x410 [i915]
<4> [188.935988]  i915_gem_wait_ioctl+0xf2/0x2a0 [i915]
<4> [188.936272]  ? i915_gem_object_wait+0x410/0x410 [i915]
<4> [188.936533]  drm_ioctl_kernel+0xae/0x140
<4> [188.936546]  drm_ioctl+0x201/0x3d0
<4> [188.936555]  ? i915_gem_object_wait+0x410/0x410 [i915]
<4> [188.936820]  ? __fget_files+0xc2/0x1c0
<4> [188.936830]  ? __fget_files+0xda/0x1c0
<4> [188.936839]  __x64_sys_ioctl+0x6d/0xa0
<4> [188.936848]  do_syscall_64+0x3a/0xb0
<4> [188.936859]  entry_SYSCALL_64_after_hwframe+0x44/0xae

If the shared object has changed during the RCU unlocked period
callers will correctly handle the restart on the next iteration.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: 96601e8a47 ("dma-buf: use new iterator in dma_resv_copy_fences")
Fixes: d3c80698c9 ("dma-buf: use new iterator in dma_resv_get_fences v3")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4274
Cc: Christian König <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20211008095007.972693-1-tvrtko.ursulin@linux.intel.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
2021-10-11 16:14:08 +02:00
..
heaps dma-buf: system_heap: Avoid warning on mid-order allocations 2021-09-14 20:25:46 +05:30
dma-buf-sysfs-stats.c dma-buf: Delete the DMA-BUF attachment sysfs statistics 2021-07-20 11:06:59 +02:00
dma-buf-sysfs-stats.h dma-buf: Delete the DMA-BUF attachment sysfs statistics 2021-07-20 11:06:59 +02:00
dma-buf.c dma-buf: use the new iterator in dma_resv_poll 2021-10-07 14:49:11 +02:00
dma-fence-array.c dma-fence: Propagate errors to dma-fence-array container 2019-08-12 08:25:52 +01:00
dma-fence-chain.c dma-buf: some dma_fence_chain improvements 2021-06-14 19:33:16 +02:00
dma-fence.c dma-buf: clarify dma_fence_add_callback documentation 2021-09-03 10:12:12 +02:00
dma-heap.c dma-buf: dma-heap: Provide accessor to get heap name 2021-02-25 18:28:24 +05:30
dma-resv.c dma-resv: Fix dma_resv_get_fences and dma_resv_copy_fences after conversion 2021-10-11 16:14:08 +02:00
Kconfig dma-buf: DMABUF_SYSFS_STATS should depend on DMA_SHARED_BUFFER 2021-09-07 12:42:21 +05:30
Makefile dma-buf: nuke seqno-fence 2021-08-16 14:07:17 +02:00
selftest.c dma-buf: Introduce selftesting framework 2019-08-19 18:01:34 +01:00
selftest.h dma-buf: Introduce selftesting framework 2019-08-19 18:01:34 +01:00
selftests.h Merge drm/drm-next into drm-intel-next-queued 2020-06-25 18:05:03 +03:00
st-dma-fence-chain.c dma-buf: add dma_fence_chain_alloc/free v3 2021-06-14 19:38:34 +02:00
st-dma-fence.c dma-buf: Avoid comma separated statements 2021-02-09 17:14:11 +01:00
sw_sync.c compat_ioctl: move more drivers to compat_ptr_ioctl 2019-10-23 17:23:44 +02:00
sync_debug.c Linux 5.2-rc5 2019-06-19 12:07:29 +02:00
sync_debug.h dma-buf: Remove unused sync_dump() 2019-04-23 09:30:07 +01:00
sync_file.c dma-buf/sync_file: Don't leak fences on merge failure 2021-07-12 13:34:49 +02:00
sync_trace.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
udmabuf.c udmabuf: fix general protection fault in udmabuf_create 2021-08-12 09:27:22 +02:00