[PATCH] btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

[PATCH] btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

[Jeff Mahoney]

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@vger.kernel.org
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
---
 fs/btrfs/ioctl.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -5653,6 +5653,10 @@ long btrfs_ioctl(struct file *file, unsi
 #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;
@@ -5663,8 +5667,6 @@ long btrfs_compat_ioctl(struct file *fil
 	case FS_IOC32_GETVERSION:
 		cmd = FS_IOC_GETVERSION;
 		break;
-	default:
-		return -ENOIOCTLCMD;
 	}
 
 	return btrfs_ioctl(file, cmd, (unsigned long) compat_ptr(arg));

-- 
Jeff Mahoney
SUSE Labs

Re: [PATCH] btrfs: fix btrfs_compat_ioctl failures on non-compat ioctls

[David Sterba]

On Mon, Feb 06, 2017 at 07:39:09PM -0500, Jeff Mahoney wrote:
> 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@vger.kernel.org
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>

Reviewed-by: David Sterba <dsterba@suse.com>