nfsd: special case truncates some more (783112f7) · Commits · 戴 / test

Both the NFS protocols and the Linux VFS use a setattr operation with a bitmap of attributes to set to set various file attributes including the file size and the uid/gid. The Linux syscalls never mix size updates with unrelated updates like the uid/gid, and some file systems like XFS and GFS2 rely on the fact that truncates don't update random other attributes, and many other file systems handle the case but do not update the other attributes in the same transaction. NFSD on the other hand passes the attributes it gets on the wire more or less directly through to the VFS, leading to updates the file systems don't expect. XFS at least has an assert on the allowed attributes, which caught an unusual NFS client setting the size and group at the same time. To handle this issue properly this splits the notify_change call in nfsd_setattr into two separate ones. Signed-off-by:

Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org Tested-by:

Chuck Lever <chuck.lever@oracle.com> Signed-off-by:

J. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

+26 −6

Original line number	Diff line number	Diff line
		@@ -414,13 +414,19 @@ nfsd_setattr(struct svc_rqst rqstp, struct svc_fh fhp, struct iattr *iap,

		/*
		* The size case is special, it changes the file in addition to the
		* attributes.
		* attributes, and file systems don't expect it to be mixed with
		* "random" attribute changes. We thus split out the size change
		* into a separate call to ->setattr, and do the rest as a separate
		* setattr call.
		*/
		if (size_change) {
		err = nfsd_get_write_access(rqstp, fhp, iap);
		if (err)
		return err;
		}

		fh_lock(fhp);
		if (size_change) {
		/*
		* RFC5661, Section 18.30.4:
		* Changing the size of a file with SETATTR indirectly
		@@ -428,16 +434,30 @@ nfsd_setattr(struct svc_rqst rqstp, struct svc_fh fhp, struct iattr *iap,
		*
		* (and similar for the older RFCs)
		*/
		if (iap->ia_size != i_size_read(inode))
		iap->ia_valid \|= ATTR_MTIME;
		struct iattr size_attr = {
		.ia_valid = ATTR_SIZE \| ATTR_CTIME \| ATTR_MTIME,
		.ia_size = iap->ia_size,
		};

		host_err = notify_change(dentry, &size_attr, NULL);
		if (host_err)
		goto out_unlock;
		iap->ia_valid &= ~ATTR_SIZE;

		/*
		* Avoid the additional setattr call below if the only other
		* attribute that the client sends is the mtime, as we update
		* it as part of the size change above.
		*/
		if ((iap->ia_valid & ~ATTR_MTIME) == 0)
		goto out_unlock;
		}

		iap->ia_valid \|= ATTR_CTIME;

		fh_lock(fhp);
		host_err = notify_change(dentry, iap, NULL);
		fh_unlock(fhp);

		out_unlock:
		fh_unlock(fhp);
		if (size_change)
		put_write_access(inode);
		out:

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