Re: [PATCH] nfsd: Return EPERM on utime/utimes/lutimes calls instead of EACCESS in some cases

J. Bruce Fields
2018-12-05T01:37:18Z

On Wed, Dec 05, 2018 at 09:04:22AM +0800, zhengbin (A) wrote:
> thanks,
> >>> As the man(3) page for utime/utimes/lutimes, EPERM is returned
>
> -------->this should be As the man page for utime/utimes/lutimes, my little mistake. utime/utimes are man(2), lutimes is man(3)
>
> I send v2 patch?Or when you apply, help modify it?

Does this look OK?

--b.

commit eb6d67589750
Author: zhengbin <zhengbin13@huawei.com>
Date: Fri Nov 30 16:04:25 2018 +0800

nfsd: Return EPERM, not EACCES, in some SETATTR cases

As the man(2) page for utime/utimes states, EPERM is returned when the
second parameter of utime/utimes/lutimes 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>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index eb67098117b4..9824e32b2f23 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -396,10 +396,23 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
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;