From ca456252db0521e5e88024fa2b67535e9739e030 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 16 Apr 2008 16:28:47 -0400 Subject: [PATCH] knfsd: clear both setuid and setgid whenever a chown is done Currently, knfsd only clears the setuid bit if the owner of a file is changed on a SETATTR call, and only clears the setgid bit if the group is changed. POSIX says this in the spec for chown(): "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 does not have appropriate privileges, the set-user-ID (S_ISUID) and set-group-ID (S_ISGID) bits of the file mode shall be cleared upon successful return from chown()." If I'm reading this correctly, then knfsd is doing this wrong. It should be clearing both the setuid and setgid bit on any SETATTR that changes the uid or gid. This wasn't really as noticable before, but now that the ATTR_KILL_S*ID bits are a no-op for the NFS client, it's more evident. This patch corrects the nfsd_setattr logic so that this occurs. It also does a bit of cleanup to the function. There is also one small behavioral change. If a SETATTR call comes in that changes the uid/gid and the mode, then we now only clear the setgid bit if the group execute bit isn't set. The setgid bit without a group execute bit signifies mandatory locking and we likely don't want to clear the bit in that case. Since there is no call in POSIX that should generate a SETATTR call like this, then this should rarely happen, but it's worth noting. Signed-off-by: Jeff Layton Signed-off-by: J. Bruce Fields --- fs/nfsd/vfs.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 1d0406c31a44..a3a291f771f4 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -359,24 +359,25 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap, DQUOT_INIT(inode); } + /* sanitize the mode change */ if (iap->ia_valid & ATTR_MODE) { iap->ia_mode &= S_IALLUGO; iap->ia_mode |= (inode->i_mode & ~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; + } + + /* Revoke setuid/setgid on chown */ + if (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) || + ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)) { + iap->ia_valid |= ATTR_KILL_PRIV; + if (iap->ia_valid & ATTR_MODE) { + /* we're setting mode too, just clear the s*id bits */ iap->ia_mode &= ~S_ISUID; + if (iap->ia_mode & S_IXGRP) + iap->ia_mode &= ~S_ISGID; + } else { + /* set ATTR_KILL_* bits and let VFS handle it */ + iap->ia_valid |= (ATTR_KILL_SUID | ATTR_KILL_SGID); } - 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; } /* Change the attributes. */ -- 2.39.5