[SRU][Trusty][Yakkety][Xenial][PATCH 1/1] btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

[Joseph Salisbury]

From: Jeff Mahoney <jeffm at suse.com>

BugLink: http://bugs.launchpad.net/bugs/1619918

Commit 4c63c2454ef incorrectly assumed that returning -ENOIOCTLCMD would
cause the native ioctl to be called.  The ->compat_ioctl callback is
expected to handle all ioctls, not just compat variants.  As a result,
when using 32-bit userspace on 64-bit kernels, everything except those
three ioctls would return -ENOTTY.

Fixes: 4c63c2454ef ("btrfs: bugfix: handle FS_IOC32_{GETFLAGS,SETFLAGS,GETVERSION} in btrfs_ioctl")
Cc: stable at vger.kernel.org
Signed-off-by: Jeff Mahoney <jeffm at suse.com>
Reviewed-by: David Sterba <dsterba at suse.com>
Signed-off-by: David Sterba <dsterba at suse.com>
(cherry picked from commit 2a362249187a8d0f6d942d6e1d763d150a296f47)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 fs/btrfs/ioctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9090ccb..ee72b30 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5678,6 +5678,10 @@ long btrfs_ioctl(struct file *file, unsigned int
 #ifdef CONFIG_COMPAT
 long btrfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
+	/*
+	 * These all access 32-bit values anyway so no further
+	 * handling is necessary.
+	 */
 	switch (cmd) {
 	case FS_IOC32_GETFLAGS:
 		cmd = FS_IOC_GETFLAGS;
@@ -5688,8 +5692,6 @@ long btrfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC32_GETVERSION:
 		cmd = FS_IOC_GETVERSION;
 		break;
-	default:
-		return -ENOIOCTLCMD;
 	}
 
 	return btrfs_ioctl(file, cmd, (unsigned long) compat_ptr(arg));
-- 
2.7.4