[PATCH 4.4-stable] jffs2: return -ERANGE when xattr buffer is too small

[Hou Tao <houtao1@xxxxxxxxxx>]

Hi Greg,

The problem had been fixed by 764a5c6b1fa4 ("xattr handlers: Simplify list
operation") in v4.5-rc1, but the modification in that commit may be too much
because it modifies all file-systems which implement xattr, so I create a single
patch for jffs2 to fix the problem. Which one is your preference ?

Hi Andreas,

Could you please help review the patch ?

Thanks,
Tao
---

From: Hou Tao <houtao1@xxxxxxxxxx>

When a file have multiple xattrs and the passed buffer is
smaller than the required size, jffs2_listxattr() should
return -ERANGE instead of continue, else Oops may occurs
due to memory corruption.

Also remove the unnecessary check ("rc < 0"), because
xhandle->list(...) will not return an error number.

Spotted by generic/377 in xfstests-dev.

Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
 fs/jffs2/xattr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 4c2c03663533..8e1427762eeb 100644
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -1004,12 +1004,14 @@ ssize_t jffs2_listxattr(struct dentry *dentry, char *buffer, size_t size)
                        rc = xhandle->list(xhandle, dentry, buffer + len,
                                           size - len, xd->xname,
                                           xd->name_len);
+                       if (rc > size - len) {
+                               rc = -ERANGE;
+                               goto out;
+                       }
                } else {
                        rc = xhandle->list(xhandle, dentry, NULL, 0,
                                           xd->xname, xd->name_len);
                }
-               if (rc < 0)
-                       goto out;
                len += rc;
        }
        rc = len;
--