From 90b0a97323f42ead278bbccbdf0e123db2add400 Mon Sep 17 00:00:00 2001 From: Carlos Maiolino 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 Signed-off-by: "Theodore Ts'o" --- 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