4.19-stable review patch. If anyone has any objections, please let me know.
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From: Josef Bacik josef@toxicpanda.com
[ Upstream commit a8892fd71933126ebae3d60aec5918d4dceaae76 ]
Our btrfs subvolume snapshot <source> <destination> utility enforces that <source> is the root of the subvolume, however this isn't enforced in the kernel. Update the kernel to also enforce this limitation to avoid problems with other users of this ioctl that don't have the appropriate checks in place.
Reported-by: Martin Michaelis code@mgjm.de CC: stable@vger.kernel.org # 4.14+ Reviewed-by: Neal Gompa neal@gompa.dev Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/ioctl.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 23beabb489231..c76277ccf03b0 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1789,6 +1789,15 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file, * are limited to own subvolumes only */ ret = -EPERM; + } else if (btrfs_ino(BTRFS_I(src_inode)) != BTRFS_FIRST_FREE_OBJECTID) { + /* + * Snapshots must be made with the src_inode referring + * to the subvolume inode, otherwise the permission + * checking above is useless because we may have + * permission on a lower directory but not the subvol + * itself. + */ + ret = -EINVAL; } else { ret = btrfs_mksubvol(&file->f_path, name, namelen, BTRFS_I(src_inode)->root,