xfs: only return -errno or success from attr ->put_listent

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@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

3 files changed, 14 insertions, 9 deletions

diff --git a/fs/xfs/xfs_attr.h b/fs/xfs/xfs_attr.h
index dd4824589470..234331227c0c 100644
--- 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 *);
 
diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
index 4fa14820e2e2..c8be331a3196 100644
--- 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_context_t *context)
                                            (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];
diff --git a/fs/xfs/xfs_xattr.c b/fs/xfs/xfs_xattr.c
index 110f1d7d86b0..f2201299311f 100644
--- a/fs/xfs/xfs_xattr.c
+++ b/fs/xfs/xfs_xattr.c
@@ -146,7 +146,7 @@ __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, prefix, prefix_len);
@@ -221,11 +221,15 @@ xfs_xattr_put_listent(
 }
 
 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);
+        struct inode    *inode = d_inode(dentry);
+        int             error;
 
         /*
          * First read the regular on-disk attributes.
@@ -239,7 +243,9 @@ xfs_vn_listxattr(struct dentry *dentry, char *data, size_t size)
         context.firstu = context.bufsize;
         context.put_listent = xfs_xattr_put_listent;
 
-        xfs_attr_list_int(&context);
+        error = xfs_attr_list_int(&context);
+        if (error)
+                return error;
         if (context.count < 0)
                 return -ERANGE;