From 90b0a97323f42ead278bbccbdf0e123db2add400 Mon Sep 17 00:00:00 2001
From: Carlos Maiolino <cmaiolino@redhat.com>
Date: Mon, 17 Sep 2012 23:39:12 -0400
Subject: [PATCH] ext4: fix possible non-initialized variable in
htree_dirblock_to_tree()
htree_dirblock_to_tree() declares a non-initialized 'err' variable,
which is passed as a reference to another functions expecting them to
set this variable with their error codes.
It's passed to ext4_bread(), which then passes it to ext4_getblk(). If
ext4_map_blocks() returns 0 due to a lookup failure, leaving the
ext4_getblk() buffer_head uninitialized, it will make ext4_getblk()
return to ext4_bread() without initialize the 'err' variable, and
ext4_bread() will return to htree_dirblock_to_tree() with this variable
still uninitialized. htree_dirblock_to_tree() will pass this variable
with garbage back to ext4_htree_fill_tree(), which expects a number of
directory entries added to the rb-tree. which, in case, might return a
fake non-zero value due the garbage left in the 'err' variable, leading
the kernel to an Oops in ext4_dx_readdir(), once this is expecting a
filled rb-tree node, when in turn it will have a NULL-ed one, causing an
invalid page request when trying to get a fname struct from this NULL-ed
rb-tree node in this line:
fname = rb_entry(info->curr_node, struct fname, rb_hash);
The patch itself initializes the err variable in
htree_dirblock_to_tree() to avoid usage mistakes by the called
functions, and also fix ext4_getblk() to return a initialized 'err'
variable when ext4_map_blocks() fails a lookup.
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/inode.c | 4 +++-
fs/ext4/namei.c | 2 +-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b4effbda7a966..ca76b5ed6c9e9 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -732,11 +732,13 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
err = ext4_map_blocks(handle, inode, &map,
create ? EXT4_GET_BLOCKS_CREATE : 0);
+ /* ensure we send some value back into *errp */
+ *errp = 0;
+
if (err < 0)
*errp = err;
if (err <= 0)
return NULL;
- *errp = 0;
bh = sb_getblk(inode->i_sb, map.m_pblk);
if (!bh) {
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 7450ff01c3c47..37c03b32e1941 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -846,7 +846,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
{
struct buffer_head *bh;
struct ext4_dir_entry_2 *de, *top;
- int err, count = 0;
+ int err = 0, count = 0;
dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n",
(unsigned long)block));
--
2.30.2