From: Alexander Lochmann alexander.lochmann@tu-dortmund.de
commit f69e749a49353d96af1a293f56b5b56de59c668a upstream.
file_remove_privs() might be called for non-regular files, e.g. blkdev inode. There is no reason to do its job on things like blkdev inodes, pipes, or cdevs. Hence, abort if file does not refer to a regular inode.
AV: more to the point, for devices there might be any number of inodes refering to given device. Which one to strip the permissions from, even if that made any sense in the first place? All of them will be observed with contents modified, after all.
Found by LockDoc (Alexander Lochmann, Horst Schirmeier and Olaf Spinczyk)
Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: Alexander Lochmann alexander.lochmann@tu-dortmund.de Signed-off-by: Horst Schirmeier horst.schirmeier@tu-dortmund.de Signed-off-by: Al Viro viro@zeniv.linux.org.uk Cc: Zubin Mithra zsm@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/inode.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/inode.c +++ b/fs/inode.c @@ -1817,8 +1817,13 @@ int file_remove_privs(struct file *file) int kill; int error = 0;
- /* Fast path for nothing security related */ - if (IS_NOSEC(inode)) + /* + * Fast path for nothing security related. + * As well for non-regular files, e.g. blkdev inodes. + * For example, blkdev_write_iter() might get here + * trying to remove privs which it is not allowed to. + */ + if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode)) return 0;
kill = dentry_needs_remove_privs(dentry);