nfsd: revoking of suid/sgid bits after chown() in a consistent way
There is an inconsistency in the handling of SUID/SGID file
bits after chown() between NFS and other local file systems.
Local file systems (for example, ext3, ext4, xfs, btrfs) revoke
SUID/SGID bits after chown() on a regular file even if
the owner/group of the file has not been changed:
~# touch file; chmod ug+s file; chmod u+x file
~# ls -l file
-rwsr-Sr-- 1 root root 0 Dec 6 04:49 file
~# chown root file; ls -l file
-rwxr-Sr-- 1 root root 0 Dec 6 04:49 file
but NFS doesn't do that:
~# touch file; chmod ug+s file; chmod u+x file
~# ls -l file
-rwsr-Sr-- 1 root root 0 Dec 6 04:49 file
~# chown root file; ls -l file
-rwsr-Sr-- 1 root root 0 Dec 6 04:49 file
NFS does that only if the owner/group has been changed:
~# touch file; chmod ug+s file; chmod u+x file
~# ls -l file
-rwsr-Sr-- 1 root root 0 Dec 6 05:02 file
~# chown bin file; ls -l file
-rwxr-Sr-- 1 bin root 0 Dec 6 05:02 file
See: http://pubs.opengroup.org/onlinepubs/9699919799/functions/chown.html
"If the specified file is a regular file, one or more of
the S_IXUSR, S_IXGRP, or S_IXOTH bits of the file mode are set,
and the process has appropriate privileges, it is
implementation-defined whether the set-user-ID and set-group-ID
bits are altered."
So both variants are acceptable by POSIX.
This patch makes NFS to behave like local file systems.
Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 7eea63c..c8aa6ff 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -348,8 +348,7 @@
/* Revoke setuid/setgid on chown */
if (!S_ISDIR(inode->i_mode) &&
- (((iap->ia_valid & ATTR_UID) && !uid_eq(iap->ia_uid, inode->i_uid)) ||
- ((iap->ia_valid & ATTR_GID) && !gid_eq(iap->ia_gid, inode->i_gid)))) {
+ ((iap->ia_valid & ATTR_UID) || (iap->ia_valid & ATTR_GID))) {
iap->ia_valid |= ATTR_KILL_PRIV;
if (iap->ia_valid & ATTR_MODE) {
/* we're setting mode too, just clear the s*id bits */