linux-kernel - [PATCH 4.4 53/53] xfs: only return -errno or success from attr ->put

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Date:   Mon,  5 Jun 2017 18:17:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Sandeen <sandeen@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Dave Chinner <david@...morbit.com>,
        Nikolay Borisov <nborisov@...e.com>
Subject: [PATCH 4.4 53/53] xfs: only return -errno or success from attr ->put_listent

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Sandeen <sandeen@...deen.net>

commit 2a6fba6d2311151598abaa1e7c9abd5f8d024a43 upstream.

Today, the put_listent formatters return either 1 or 0; if
they return 1, some callers treat this as an error and return
it up the stack, despite "1" not being a valid (negative)
error code.

The intent seems to be that if the input buffer is full,
we set seen_enough or set count = -1, and return 1;
but some callers check the return before checking the
seen_enough or count fields of the context.

Fix this by only returning non-zero for actual errors
encountered, and rely on the caller to first check the
return value, then check the values in the context to
decide what to do.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Dave Chinner <david@...morbit.com>
Signed-off-by: Nikolay Borisov <nborisov@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/xfs/xfs_attr.h      |    1 +
 fs/xfs/xfs_attr_list.c |    8 +++-----
 fs/xfs/xfs_xattr.c     |   15 ++++++++++-----
 3 files changed, 14 insertions(+), 10 deletions(-)

--- a/fs/xfs/xfs_attr.h
+++ b/fs/xfs/xfs_attr.h
@@ -112,6 +112,7 @@ typedef struct attrlist_cursor_kern {
  *========================================================================*/
 
 
+/* Return 0 on success, or -errno; other state communicated via *context */
 typedef int (*put_listent_func_t)(struct xfs_attr_list_context *, int,
 			      unsigned char *, int, int, unsigned char *);
 
--- a/fs/xfs/xfs_attr_list.c
+++ b/fs/xfs/xfs_attr_list.c
@@ -108,16 +108,14 @@ xfs_attr_shortform_list(xfs_attr_list_co
 					   (int)sfe->namelen,
 					   (int)sfe->valuelen,
 					   &sfe->nameval[sfe->namelen]);
-
+			if (error)
+				return error;
 			/*
 			 * Either search callback finished early or
 			 * didn't fit it all in the buffer after all.
 			 */
 			if (context->seen_enough)
 				break;
-
-			if (error)
-				return error;
 			sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 		}
 		trace_xfs_attr_list_sf_all(context);
@@ -581,7 +579,7 @@ xfs_attr_put_listent(
 		trace_xfs_attr_list_full(context);
 		alist->al_more = 1;
 		context->seen_enough = 1;
-		return 1;
+		return 0;
 	}
 
 	aep = (attrlist_ent_t *)&context->alist[context->firstu];
--- a/fs/xfs/xfs_xattr.c
+++ b/fs/xfs/xfs_xattr.c
@@ -180,7 +180,7 @@ xfs_xattr_put_listent(
 	arraytop = context->count + prefix_len + namelen + 1;
 	if (arraytop > context->firstu) {
 		context->count = -1;	/* insufficient space */
-		return 1;
+		return 0;
 	}
 	offset = (char *)context->alist + context->count;
 	strncpy(offset, xfs_xattr_prefix(flags), prefix_len);
@@ -222,12 +222,15 @@ list_one_attr(const char *name, const si
 }
 
 ssize_t
-xfs_vn_listxattr(struct dentry *dentry, char *data, size_t size)
+xfs_vn_listxattr(
+	struct dentry	*dentry,
+	char		*data,
+	size_t		size)
 {
 	struct xfs_attr_list_context context;
 	struct attrlist_cursor_kern cursor = { 0 };
-	struct inode		*inode = d_inode(dentry);
-	int			error;
+	struct inode	*inode = d_inode(dentry);
+	int		error;
 
 	/*
 	 * First read the regular on-disk attributes.
@@ -245,7 +248,9 @@ xfs_vn_listxattr(struct dentry *dentry,
 	else
 		context.put_listent = xfs_xattr_put_listent_sizes;
 
-	xfs_attr_list_int(&context);
+	error = xfs_attr_list_int(&context);
+	if (error)
+		return error;
 	if (context.count < 0)
 		return -ERANGE;