From: Miklos Szeredi mszeredi@redhat.com
commit b24e7598db62386a95a3c8b9c75630c5d56fe077 upstream.
If writeback cache is enabled, then writes might get reordered with chmod/chown/utimes. The problem with this is that performing the write in the fuse daemon might itself change some of these attributes. In such case the following sequence of operations will result in file ending up with the wrong mode, for example:
int fd = open ("suid", O_WRONLY|O_CREAT|O_EXCL); write (fd, "1", 1); fchown (fd, 0, 0); fchmod (fd, 04755); close (fd);
This patch fixes this by flushing pending writes before performing chown/chmod/utimes.
Reported-by: Giuseppe Scrivano gscrivan@redhat.com Tested-by: Giuseppe Scrivano gscrivan@redhat.com Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on") Cc: stable@vger.kernel.org # v3.15+ Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fuse/dir.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1650,6 +1650,19 @@ int fuse_do_setattr(struct dentry *dentr if (attr->ia_valid & ATTR_SIZE) is_truncate = true;
+ /* Flush dirty data/metadata before non-truncate SETATTR */ + if (is_wb && S_ISREG(inode->i_mode) && + attr->ia_valid & + (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_MTIME_SET | + ATTR_TIMES_SET)) { + err = write_inode_now(inode, true); + if (err) + return err; + + fuse_set_nowrite(inode); + fuse_release_nowrite(inode); + } + if (is_truncate) { fuse_set_nowrite(inode); set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);