From 72c913fdde9da6bbad5254b7317efd2000ee6ddb Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 23 Oct 2019 14:26:37 +0200 Subject: [PATCH] fuse: flush dirty data/metadata before non-truncate setattr 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 Tested-by: Giuseppe Scrivano Fixes: 4d99ff8f12eb ("fuse: Turn writeback cache on") Cc: # v3.15+ Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- fs/fuse/dir.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 82a13221775e..e7a2a988533d 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1665,6 +1665,19 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr, 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);