From: zhengbin <zhengbin13@huawei.com>
Date: Fri, 30 Nov 2018 16:04:25 +0800
Subject: [PATCH] nfsd: Return EPERM, not EACCES, in some SETATTR cases
Git-commit: 255fbca65137e25b12bced18ec9a014dc77ecda0
Patch-mainline: v5.0
References: git-fixes

As the man(2) page for utime/utimes states, EPERM is returned when the
second parameter of utime or utimes is not NULL, the caller's effective UID
does not match the owner of the file, and the caller is not privileged.

However, in a NFS directory mounted from knfsd, it will return EACCES
(from nfsd_setattr-> fh_verify->nfsd_permission).  This patch fixes
that.

Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfsd/vfs.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -395,10 +395,23 @@ nfsd_setattr(struct svc_rqst *rqstp, str
 	bool		get_write_count;
 	bool		size_change = (iap->ia_valid & ATTR_SIZE);
 
-	if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME | ATTR_SIZE))
+	if (iap->ia_valid & ATTR_SIZE) {
 		accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
-	if (iap->ia_valid & ATTR_SIZE)
 		ftype = S_IFREG;
+	}
+
+	/*
+	 * If utimes(2) and friends are called with times not NULL, we should
+	 * not set NFSD_MAY_WRITE bit. Otherwise fh_verify->nfsd_permission
+	 * will return EACCESS, when the caller's effective UID does not match
+	 * the owner of the file, and the caller is not privileged. In this
+	 * situation, we should return EPERM(notify_change will return this).
+	 */
+	if (iap->ia_valid & (ATTR_ATIME | ATTR_MTIME)) {
+		accmode |= NFSD_MAY_OWNER_OVERRIDE;
+		if (!(iap->ia_valid & (ATTR_ATIME_SET | ATTR_MTIME_SET)))
+			accmode |= NFSD_MAY_WRITE;
+	}
 
 	/* Callers that do fh_verify should do the fh_want_write: */
 	get_write_count = !fhp->fh_dentry;