Commit 0fd9da9a authored May 27, 2016 by Nicolai Stange Committed by Greg Kroah-Hartman Jun 17, 2016

staging/android: sync_debug: unproxify debugfs files' fops



Since commit 49d200de ("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 a44eb74c ("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: 49d200de ("debugfs: prevent access to removed files' private data")
Fixes: a44eb74c ("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>

parent b1f65604

drivers/staging/android/sync_debug.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -189,9 +189,14 @@ 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,
		/*
		* 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;