From: Goldwyn Rodrigues rgoldwyn@suse.de
stable inclusion from stable-v5.10.140 commit d2bd18d50c1e835d154e018adb8f56d35d622528 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I63FTT
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit b51111271b0352aa596c5ae8faf06939e91b3b68 upstream.
For a filesystem which has btrfs read-only property set to true, all write operations including xattr should be denied. However, security xattr can still be changed even if btrfs ro property is true.
This happens because xattr_permission() does not have any restrictions on security.*, system.* and in some cases trusted.* from VFS and the decision is left to the underlying filesystem. See comments in xattr_permission() for more details.
This patch checks if the root is read-only before performing the set xattr operation.
Testcase:
DEV=/dev/vdb MNT=/mnt
mkfs.btrfs -f $DEV mount $DEV $MNT echo "file one" > $MNT/f1
setfattr -n "security.one" -v 2 $MNT/f1 btrfs property set /mnt ro true
setfattr -n "security.one" -v 1 $MNT/f1
umount $MNT
CC: stable@vger.kernel.org # 4.9+ Reviewed-by: Qu Wenruo wqu@suse.com Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Goldwyn Rodrigues rgoldwyn@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com Reviewed-by: Wei Li liwei391@huawei.com --- fs/btrfs/xattr.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c index f1a60bcdb3db..cd6049b0bde5 100644 --- a/fs/btrfs/xattr.c +++ b/fs/btrfs/xattr.c @@ -389,6 +389,9 @@ static int btrfs_xattr_handler_set(const struct xattr_handler *handler, const char *name, const void *buffer, size_t size, int flags) { + if (btrfs_root_readonly(BTRFS_I(inode)->root)) + return -EROFS; + name = xattr_full_name(handler, name); return btrfs_setxattr_trans(inode, name, buffer, size, flags); }