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accel/amdxdna: return early from a zero-length flush

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SYNC_BO does not constrain its size, so a request for zero bytes reaches
drm_clflush_virt_range(), which ends with an unconditional
clflushopt(end - 1). For an empty range that is the byte before the
mapping, and abo->mem.kva comes from vmap(), so the access lands in the
guard page below the vmalloc area and faults:

  BUG: unable to handle page fault for address: ffffd16fbbc70fff
  #PF: supervisor read access in kernel mode
  Oops: Oops: 0000 [#1] SMP NOPTI
  CPU: 7 UID: 1000 Comm: sync_bo_probe
  RIP: 0010:drm_clflush_virt_range+0x3c/0x70
  Call Trace:
   amdxdna_drm_sync_bo_ioctl+0x124/0x430 [amdxdna]
   drm_ioctl+0x301/0x4c0
   __x64_sys_ioctl+0x115/0x2f0
   do_syscall_64+0xa6/0x3d0

Any process that can open the render node can do this. Reproduced 3 of 3
times on a Strix Point NPU (1022:17f0), by calling SYNC_BO with size 0 on
an AMDXDNA_BO_SHARE object. The import arm takes the same request but
flushes the whole scatterlist, so it survives it.

Nothing needs flushing for an empty range, so answer before choosing a
path.

Fixes: e252e3f348 ("accel/amdxdna: Revise device bo creation and free")
Cc: stable@vger.kernel.org
Signed-off-by: Taimuraz Kaitmazov <taimuraz@kaitmazov.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260817230655.356785-1-taimuraz@kaitmazov.com
This commit is contained in:
Taimuraz Kaitmazov 2026-08-18 02:06:55 +03:00 committed by Lizhi Hou
parent ab243f74ab
commit dc14753664
1 changed files with 3 additions and 0 deletions
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3
drivers/accel/amdxdna/amdxdna_gem.c
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@ -1247,6 +1247,9 @@ static int amdxdna_flush_bo(struct amdxdna_gem_obj *abo, u64 offset, u64 size)
return -EINVAL;
size = min(abo->mem.size, end) - offset;
if (!size)
return 0;
if (is_import_bo(abo))
drm_clflush_sg(abo->base.sgt);
else if (amdxdna_gem_vmap(abo))