Commit 4ac35c2f authored Feb 10, 2009 by wengang wang Committed by J. Bruce Fields Mar 18, 2009

nfsd(v2/v3): fix the failure of creation from HPUX client



sometimes HPUX nfs client sends a create request to linux nfs server(v2/v3).
the dump of the request is like:
    obj_attributes
        mode: value follows
            set_it: value follows (1)
            mode: 00
        uid: no value
            set_it: no value (0)
        gid: value follows
            set_it: value follows (1)
            gid: 8030
        size: value follows
            set_it: value follows (1)
            size: 0
        atime: don't change
            set_it: don't change (0)
        mtime: don't change
            set_it: don't change (0)

note that mode is 00(havs no rwx privilege even for the owner) and it requires
to set size to 0.

as current nfsd(v2/v3) implementation, the server does mainly 2 steps:
1) creates the file in mode specified by calling vfs_create().
2) sets attributes for the file by calling nfsd_setattr().

at step 2), it finally calls file system specific setattr() function which may
fail when checking permission because changing size needs WRITE privilege but
it has none since mode is 000.

for this case, a new file created, we may simply ignore the request of
setting size to 0, so that WRITE privilege is not needed and the open
succeeds.

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
--
 vfs.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

parent e33d1ea6

fs/nfsd/vfs.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -1176,6 +1176,21 @@ nfsd_create_setattr(struct svc_rqst rqstp, struct svc_fh resfhp,
		return 0;
		}

		/* HPUX client sometimes creates a file in mode 000, and sets size to 0.
		* setting size to 0 may fail for some specific file systems by the permission
		* checking which requires WRITE permission but the mode is 000.
		* we ignore the resizing(to 0) on the just new created file, since the size is
		* 0 after file created.
		*
		* call this only after vfs_create() is called.
		* */
		static void
		nfsd_check_ignore_resizing(struct iattr *iap)
		{
		if ((iap->ia_valid & ATTR_SIZE) && (iap->ia_size == 0))
		iap->ia_valid &= ~ATTR_SIZE;
		}

		/*
		* Create a file (regular, directory, device, fifo); UNIX sockets
		* not yet implemented.
		@@ -1271,6 +1286,8 @@ nfsd_create(struct svc_rqst rqstp, struct svc_fh fhp,
		switch (type) {
		case S_IFREG:
		host_err = vfs_create(dirp, dchild, iap->ia_mode, NULL);
		if (!host_err)
		nfsd_check_ignore_resizing(iap);
		break;
		case S_IFDIR:
		host_err = vfs_mkdir(dirp, dchild, iap->ia_mode);
		@@ -1424,6 +1441,8 @@ nfsd_create_v3(struct svc_rqst rqstp, struct svc_fh fhp,
		/* setattr will sync the child (or not) */
		}

		nfsd_check_ignore_resizing(iap);

		if (createmode == NFS3_CREATE_EXCLUSIVE) {
		/* Cram the verifier into atime/mtime */
		iap->ia_valid = ATTR_MTIME\|ATTR_ATIME

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