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 thei 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@xxxxxxxxxx>
---
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 dff171c..41079f4 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 2a42cc0..262f863 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -839,7 +839,7 @@ 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));
--
1.7.11.4
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
