From bb289b7be62db84b9630ce00367444c810cada2c Mon Sep 17 00:00:00 2001 From: Omar Sandoval Date: Mon, 18 May 2015 02:16:29 -0700 Subject: [PATCH] Btrfs: fail on mismatched subvol and subvolid mount options There's nothing to stop a user from passing both subvol= and subvolid= to mount, but if they don't refer to the same subvolume, someone is going to be surprised at some point. Error out on this case, but allow users to pass in both if they do match (which they could, for example, get out of /proc/mounts). Reviewed-by: David Sterba Signed-off-by: Omar Sandoval Signed-off-by: Chris Mason --- fs/btrfs/super.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index dd89dd353c4a..3ad97953537c 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1167,8 +1167,9 @@ static char *setup_root_args(char *args) return buf; } -static struct dentry *mount_subvol(const char *subvol_name, int flags, - const char *device_name, char *data) +static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid, + int flags, const char *device_name, + char *data) { struct dentry *root; struct vfsmount *mnt = NULL; @@ -1214,12 +1215,27 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, /* mount_subtree() drops our reference on the vfsmount. */ mnt = NULL; - if (!IS_ERR(root) && !is_subvolume_inode(d_inode(root))) { + if (!IS_ERR(root)) { struct super_block *s = root->d_sb; - dput(root); - root = ERR_PTR(-EINVAL); - deactivate_locked_super(s); - pr_err("BTRFS: '%s' is not a valid subvolume\n", subvol_name); + struct inode *root_inode = d_inode(root); + u64 root_objectid = BTRFS_I(root_inode)->root->root_key.objectid; + + ret = 0; + if (!is_subvolume_inode(root_inode)) { + pr_err("BTRFS: '%s' is not a valid subvolume\n", + subvol_name); + ret = -EINVAL; + } + if (subvol_objectid && root_objectid != subvol_objectid) { + pr_err("BTRFS: subvol '%s' does not match subvolid %llu\n", + subvol_name, subvol_objectid); + ret = -EINVAL; + } + if (ret) { + dput(root); + root = ERR_PTR(ret); + deactivate_locked_super(s); + } } out: @@ -1312,7 +1328,8 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, if (subvol_name) { /* mount_subvol() will free subvol_name. */ - return mount_subvol(subvol_name, flags, device_name, data); + return mount_subvol(subvol_name, subvol_objectid, flags, + device_name, data); } security_init_mnt_opts(&new_sec_opts); -- 2.20.1