From: Miklos Szeredi Date: Tue, 6 Dec 2016 15:18:45 +0000 (+0100) Subject: fuse: fix clearing suid, sgid for chown() X-Git-Tag: v4.8.15~30 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6e284445bab5b205e6b6e40f5186b18c4e7fd800;p=thirdparty%2Fkernel%2Fstable.git fuse: fix clearing suid, sgid for chown() commit c01638f5d919728f565bf8b5e0a6a159642df0d9 upstream. Basically, the pjdfstests set the ownership of a file to 06555, and then chowns it (as root) to a new uid/gid. Prior to commit a09f99eddef4 ("fuse: fix killing s[ug]id in setattr"), fuse would send down a setattr with both the uid/gid change and a new mode. Now, it just sends down the uid/gid change. Technically this is NOTABUG, since POSIX doesn't _require_ that we clear these bits for a privileged process, but Linux (wisely) has done that and I think we don't want to change that behavior here. This is caused by the use of should_remove_suid(), which will always return 0 when the process has CAP_FSETID. In fact we really don't need to be calling should_remove_suid() at all, since we've already been indicated that we should remove the suid, we just don't want to use a (very) stale mode for that. This patch should fix the above as well as simplify the logic. Reported-by: Jeff Layton Signed-off-by: Miklos Szeredi Fixes: a09f99eddef4 ("fuse: fix killing s[ug]id in setattr") Reviewed-by: Jeff Layton Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 4ff9251e9d3ab..eb5373a026e33 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1709,8 +1709,6 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) return -EACCES; if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) { - int kill; - attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_MODE); /* @@ -1722,12 +1720,11 @@ static int fuse_setattr(struct dentry *entry, struct iattr *attr) return ret; attr->ia_mode = inode->i_mode; - kill = should_remove_suid(entry); - if (kill & ATTR_KILL_SUID) { + if (inode->i_mode & S_ISUID) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISUID; } - if (kill & ATTR_KILL_SGID) { + if ((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) { attr->ia_valid |= ATTR_MODE; attr->ia_mode &= ~S_ISGID; }