[PATCH 5.17 645/772] ext4: verify dir block before splitting it

Greg Kroah-Hartman
2022-06-07T21:54:34Z

From: Jan Kara <jack@suse.cz>

commit 46c116b920ebec58031f0a78c5ea9599b0d2a371 upstream.

Before splitting a directory block verify its directory entries are sane
so that the splitting code does not access memory it should not.

Cc: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220518093332.13986-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ext4/namei.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)

--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -277,9 +277,9 @@ static struct dx_frame *dx_probe(struct
struct dx_hash_info *hinfo,
struct dx_frame *frame);
static void dx_release(struct dx_frame *frames);
-static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de,
- unsigned blocksize, struct dx_hash_info *hinfo,
- struct dx_map_entry map[]);
+static int dx_make_map(struct inode *dir, struct buffer_head *bh,
+ struct dx_hash_info *hinfo,
+ struct dx_map_entry *map_tail);
static void dx_sort_map(struct dx_map_entry *map, unsigned count);
static struct ext4_dir_entry_2 *dx_move_dirents(struct inode *dir, char *from,
char *to, struct dx_map_entry *offsets,
@@ -1249,15 +1249,23 @@ static inline int search_dirblock(struct
* Create map of hash values, offsets, and sizes, stored at end of block.
* Returns number of entries mapped.
*/
-static int dx_make_map(struct inode *dir, struct ext4_dir_entry_2 *de,
- unsigned blocksize, struct dx_hash_info *hinfo,
+static int dx_make_map(struct inode *dir, struct buffer_head *bh,
+ struct dx_hash_info *hinfo,
struct dx_map_entry *map_tail)
{
int count = 0;
- char *base = (char *) de;
+ struct ext4_dir_entry_2 *de = (struct ext4_dir_entry_2 *)bh->b_data;
+ unsigned int buflen = bh->b_size;
+ char *base = bh->b_data;
struct dx_hash_info h = *hinfo;

- while ((char *) de < base + blocksize) {
+ if (ext4_has_metadata_csum(dir->i_sb))
+ buflen -= sizeof(struct ext4_dir_entry_tail);
+
+ while ((char *) de < base + buflen) {
+ if (ext4_check_dir_entry(dir, NULL, de, bh, base, buflen,
+ ((char *)de) - base))
+ return -EFSCORRUPTED;
if (de->name_len && de->inode) {
if (ext4_hash_in_dirent(dir))
h.hash = EXT4_DIRENT_HASH(de);
@@ -1270,8 +1278,7 @@ static int dx_make_map(struct inode *dir
count++;
cond_resched();
}
- /* XXX: do we need to check rec_len == 0 case? -Chris */
- de = ext4_next_entry(de, blocksize);
+ de = ext4_next_entry(de, dir->i_sb->s_blocksize);
}
return count;
}
@@ -1943,8 +1950,11 @@ static struct ext4_dir_entry_2 *do_split

/* create map in the end of data2 block */
map = (struct dx_map_entry *) (data2 + blocksize);
- count = dx_make_map(dir, (struct ext4_dir_entry_2 *) data1,
- blocksize, hinfo, map);
+ count = dx_make_map(dir, *bh, hinfo, map);
+ if (count < 0) {
+ err = count;
+ goto journal_error;
+ }
map -= count;
dx_sort_map(map, count);
/* Ensure that neither split block is over half full */