knfsd: only set ATTR_KILL_S*ID if ATTR_MODE isn't being explicitly set

It's theoretically possible for a single SETATTR call to come in that sets the
mode and the uid/gid.  In that case, don't set the ATTR_KILL_S*ID bits since
that would trip the BUG() in notify_change.  Just fix up the mode to have the
same effect.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Cc: Neil Brown <neilb@suse.de>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 6 deletions

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 819545d21670..46934c97f8f7 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -364,14 +364,23 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
         if (iap->ia_valid & ATTR_MODE) {
                 iap->ia_mode &= S_IALLUGO;
                 imode = iap->ia_mode |= (imode & ~S_IALLUGO);
+                /* if changing uid/gid revoke setuid/setgid in mode */
+                if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) {
+                        iap->ia_valid |= ATTR_KILL_PRIV;
+                        iap->ia_mode &= ~S_ISUID;
+                }
+                if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
+                        iap->ia_mode &= ~S_ISGID;
+        } else {
+                /*
+                 * Revoke setuid/setgid bit on chown/chgrp
+                 */
+                if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid)
+                        iap->ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV;
+                if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
+                        iap->ia_valid |= ATTR_KILL_SGID;
         }
 
-        /* Revoke setuid/setgid bit on chown/chgrp */
-        if ((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid)
-                iap->ia_valid |= ATTR_KILL_SUID | ATTR_KILL_PRIV;
-        if ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)
-                iap->ia_valid |= ATTR_KILL_SGID;
-
         /* Change the attributes. */
 
         iap->ia_valid |= ATTR_CTIME;