[PATCH v2 07/25] ext4: drop ppath from ext4_ext_replay_update_ex() to avoid double-free

libaokun
2024-08-22T02:40:37Z

When calling ext4_force_split_extent_at() in ext4_ext_replay_update_ex(),
the 'ppath' is updated but it is the 'path' that is freed, thus potentially
triggering a double-free in the following process:

ext4_ext_replay_update_ex
ppath = path
ext4_force_split_extent_at(&ppath)
ext4_split_extent_at
ext4_ext_insert_extent
ext4_ext_create_new_leaf
ext4_ext_grow_indepth
ext4_find_extent
if (depth > path[0].p_maxdepth)
kfree(path) ---> path First freed
*orig_path = path = NULL ---> null ppath
kfree(path) ---> path double-free !!!

So drop the unnecessary ppath and use path directly to avoid this problem.
And use ext4_find_extent() directly to update path, avoiding unnecessary
memory allocation and freeing. Also, propagate the error returned by
ext4_find_extent() instead of using strange error codes.

Fixes: 8016e29f4362 ("ext4: fast commit recovery path")
Cc: stable@kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
fs/ext4/extents.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 91c6586afcca..cd2e71123a25 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5921,7 +5921,7 @@ int ext4_clu_mapped(struct inode *inode, ext4_lblk_t lclu)
int ext4_ext_replay_update_ex(struct inode *inode, ext4_lblk_t start,
int len, int unwritten, ext4_fsblk_t pblk)
{
- struct ext4_ext_path *path = NULL, *ppath;
+ struct ext4_ext_path *path;
struct ext4_extent *ex;
int ret;

@@ -5937,30 +5937,29 @@ int ext4_ext_replay_update_ex(struct inode *inode, ext4_lblk_t start,
if (le32_to_cpu(ex->ee_block) != start ||
ext4_ext_get_actual_len(ex) != len) {
/* We need to split this extent to match our extent first */
- ppath = path;
down_write(&EXT4_I(inode)->i_data_sem);
- ret = ext4_force_split_extent_at(NULL, inode, &ppath, start, 1);
+ ret = ext4_force_split_extent_at(NULL, inode, &path, start, 1);
up_write(&EXT4_I(inode)->i_data_sem);
if (ret)
goto out;
- kfree(path);
- path = ext4_find_extent(inode, start, NULL, 0);
+
+ path = ext4_find_extent(inode, start, &path, 0);
if (IS_ERR(path))
- return -1;
- ppath = path;
+ return PTR_ERR(path);
ex = path[path->p_depth].p_ext;
WARN_ON(le32_to_cpu(ex->ee_block) != start);
+
if (ext4_ext_get_actual_len(ex) != len) {
down_write(&EXT4_I(inode)->i_data_sem);
- ret = ext4_force_split_extent_at(NULL, inode, &ppath,
+ ret = ext4_force_split_extent_at(NULL, inode, &path,
start + len, 1);
up_write(&EXT4_I(inode)->i_data_sem);
if (ret)
goto out;
- kfree(path);
- path = ext4_find_extent(inode, start, NULL, 0);
+
+ path = ext4_find_extent(inode, start, &path, 0);
if (IS_ERR(path))
- return -EINVAL;
+ return PTR_ERR(path);
ex = path[path->p_depth].p_ext;
}
}
--
2.39.2