As we close a handle GEM object, we update the drm_file's idr with an error pointer to indicate the in-progress closure, and finally set it to NULL. If we read the idr directly, we may then see an invalid object pointer, and in our debugfs per_file_stats() we therefore need to protect against the entry being invalid.
[ 1016.651637] RIP: 0010:per_file_stats+0xe/0x16e [ 1016.651646] Code: d2 41 0f b6 8e 69 8c 00 00 48 89 df 48 c7 c6 7b 74 8c be 31 c0 e8 0c 89 cf ff eb d2 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 53 <8b> 06 85 c0 0f 84 4d 01 00 00 49 89 d6 48 89 f3 3d ff ff ff 7f 73 [ 1016.651651] RSP: 0018:ffffad3a01337ba0 EFLAGS: 00010293 [ 1016.651656] RAX: 0000000000000018 RBX: ffff96fe040d65e0 RCX: 0000000000000002 [ 1016.651660] RDX: ffffad3a01337c50 RSI: 0000000000000000 RDI: 00000000000001e8 [ 1016.651663] RBP: ffffad3a01337bb8 R08: 0000000000000000 R09: 00000000000001c0 [ 1016.651667] R10: 0000000000000000 R11: ffffffffbdbe5fce R12: 0000000000000000 [ 1016.651671] R13: ffffffffbdbe5fce R14: ffffad3a01337c50 R15: 0000000000000001 [ 1016.651676] FS: 00007a597e2d7480(0000) GS:ffff96ff3bb00000(0000) knlGS:0000000000000000 [ 1016.651680] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1016.651683] CR2: 0000000000000000 CR3: 0000000171fc2001 CR4: 00000000003606e0 [ 1016.651687] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 1016.651690] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 1016.651693] Call Trace: [ 1016.651693] Call Trace: [ 1016.651703] idr_for_each+0x8a/0xe8 [ 1016.651711] i915_gem_object_info+0x2a3/0x3eb [ 1016.651720] seq_read+0x162/0x3ca [ 1016.651727] full_proxy_read+0x5b/0x8d [ 1016.651733] __vfs_read+0x45/0x1bb [ 1016.651741] vfs_read+0xc9/0x15e [ 1016.651746] ksys_read+0x7e/0xde [ 1016.651752] do_syscall_64+0x54/0x68 [ 1016.651758] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Reported-by: Guenter Roeck linux@roeck-us.net Fixes: a8c15954d64a ("drm/i915: Protect debugfs per_file_stats with RCU lock") Signed-off-by: Chris Wilson chris@chris-wilson.co.uk Cc: Mika Kuoppala mika.kuoppala@linux.intel.com Cc: Guenter Roeck linux@roeck-us.net Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/i915_debugfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index 8594a8ef08ce..9ca94a435b75 100644 --- a/drivers/gpu/drm/i915/i915_debugfs.c +++ b/drivers/gpu/drm/i915/i915_debugfs.c @@ -230,7 +230,7 @@ static int per_file_stats(int id, void *ptr, void *data) struct file_stats *stats = data; struct i915_vma *vma;
- if (!kref_get_unless_zero(&obj->base.refcount)) + if (IS_ERR_OR_NULL(obj) || !kref_get_unless_zero(&obj->base.refcount)) return 0;
stats->count++;