As we close GEM object and set file_priv to -EBADF which is protected by ctx->mutex, populating the GEM debugfs info is not protected and results in the crash shown below.
Make sure to protect the access to file_priv using ctx->mutex to avoid race.
BUG: unable to handle page fault for address: ffffffffffffffff RIP: 0010:i915_gem_object_info+0x26b/0x3eb Code: 89 44 24 48 48 89 44 24 40 48 89 44 24 38 48 89 44 24 30 48 89 44 24 28 48 89 44 24 20 49 8b 46 f0 48 89 44 24 20 49 8b 46 a0 <48> 8b 58 08 b9 0a 00 00 00 48 b8 aa aa aa aa aa aa aa aa 48 8d bc RSP: 0018:ffffac81c14cfc30 EFLAGS: 00010246 RAX: fffffffffffffff7 RBX: ffff95094429c218 RCX: ffff95096756c740 RDX: 0000000000000000 RSI: ffffffff919b93ee RDI: ffff95094429c218 RBP: ffffac81c14cfd58 R08: ffff9509746fab80 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff9509753f8e80 R13: ffffac81c14cfc98 R14: ffff95094429c268 R15: ffffac81c14cfc88 FS: 00007a1bdcd52900(0000) GS:ffff950977e00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffff CR3: 000000026b4e0000 CR4: 0000000000340ef0 Call Trace: seq_read+0x162/0x3ca full_proxy_read+0x5b/0x8d __vfs_read+0x45/0x1b9 vfs_read+0xc9/0x15e ksys_read+0x7e/0xde do_syscall_64+0x54/0x7e entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7a1bdd34cf03
Signed-off-by: Nikunj A. Dadhania nikunj.dadhania@linux.intel.com Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/i915_debugfs.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index 784219962193..ea469168cd44 100644 --- a/drivers/gpu/drm/i915/i915_debugfs.c +++ b/drivers/gpu/drm/i915/i915_debugfs.c @@ -326,6 +326,7 @@ static void print_context_stats(struct seq_file *m, } i915_gem_context_unlock_engines(ctx);
+ mutex_lock(&ctx->mutex); if (!IS_ERR_OR_NULL(ctx->file_priv)) { struct file_stats stats = { .vm = rcu_access_pointer(ctx->vm), @@ -346,6 +347,7 @@ static void print_context_stats(struct seq_file *m,
print_file_stats(m, name, stats); } + mutex_unlock(&ctx->mutex);
spin_lock(&i915->gem.contexts.lock); list_safe_reset_next(ctx, cn, link);