staging/android: sync_debug: unproxify debugfs files' fops

Since commit 49d200deaa68 ("debugfs: prevent access to removed files'
private data"), a debugfs file's file_operations methods get proxied
through lifetime aware wrappers.

However, only a certain subset of the file_operations members is supported
by debugfs and ->compat_ioctl isn't among them -- it appears to be NULL
from the VFS layer's perspective.

This behaviour breaks the /sys/kernel/debug/sync/sw_sync file introduced
concurrently with commit a44eb74cd413 ("staging/android: move SW_SYNC_USER
to a debugfs file").

Since that file never gets removed, there is no file removal race and thus,
a lifetime checking proxy isn't needed.

Avoid the proxying for /sys/kernel/debug/sync/sw_sync by creating it via
debugfs_create_file_unsafe() rather than debugfs_create_file().
For consistency, do the same for /sys/kernel/debug/sync/info.

Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data")
Fixes: a44eb74cd413 ("staging/android: move SW_SYNC_USER to a debugfs file")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/android/sync_debug.c b/drivers/staging/android/sync_debug.c
index 903296988d416cabb6222c0d26920cd709ea1930..4c5a85595a85b7d6339804d20a80a42b0aa5eabf 100644 (file)
--- a/drivers/staging/android/sync_debug.c
+++ b/drivers/staging/android/sync_debug.c
@@ -189,10 +189,15 @@ static __init int sync_debugfs_init(void)
 {
        dbgfs = debugfs_create_dir("sync", NULL);
 
-       debugfs_create_file("info", 0444, dbgfs, NULL, &sync_info_debugfs_fops);
-
-       debugfs_create_file("sw_sync", 0644, dbgfs, NULL,
-                           &sw_sync_debugfs_fops);
+       /*
+        * The debugfs files won't ever get removed and thus, there is
+        * no need to protect it against removal races. The use of
+        * debugfs_create_file_unsafe() is actually safe here.
+        */
+       debugfs_create_file_unsafe("info", 0444, dbgfs, NULL,
+                                  &sync_info_debugfs_fops);
+       debugfs_create_file_unsafe("sw_sync", 0644, dbgfs, NULL,
+                                  &sw_sync_debugfs_fops);
 
        return 0;
 }