ext4: update orig_path in ext4_find_extent()
commit 5b4b2dcace35f618fe361a87bae6f0d13af31bc1 upstream.
In ext4_find_extent(), if the path is not big enough, we free it and set
*orig_path to NULL. But after reallocating and successfully initializing
the path, we don't update *orig_path, in which case the caller gets a
valid path but a NULL ppath, and this may cause a NULL pointer dereference
or a path memory leak. For example:
ext4_split_extent
path = *ppath = 2000
ext4_find_extent
if (depth > path[0].p_maxdepth)
kfree(path = 2000);
*orig_path = path = NULL;
path = kcalloc() = 3000
ext4_split_extent_at(*ppath = NULL)
path = *ppath;
ex = path[depth].p_ext;
// NULL pointer dereference!
==================================================================
BUG: kernel NULL pointer dereference, address: 0000000000000010
CPU: 6 UID: 0 PID: 576 Comm: fsstress Not tainted 6.11.0-rc2-dirty #847
RIP: 0010:ext4_split_extent_at+0x6d/0x560
Call Trace:
<TASK>
ext4_split_extent.isra.0+0xcb/0x1b0
ext4_ext_convert_to_initialized+0x168/0x6c0
ext4_ext_handle_unwritten_extents+0x325/0x4d0
ext4_ext_map_blocks+0x520/0xdb0
ext4_map_blocks+0x2b0/0x690
ext4_iomap_begin+0x20e/0x2c0
[...]
==================================================================
Therefore, *orig_path is updated when the extent lookup succeeds, so that
the caller can safely use path or *ppath.
BUG=b/375751183
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2024-49881 in the Linux kernel.
cos-patch: security-moderate
Change-Id: I7b70f2b0895fa30771fc35a80fb529d7687f3d4b
Signed-off-by: Arnav Kansal <rnv@google.com>
Fixes: 10809df84a4d ("ext4: teach ext4_ext_find_extent() to realloc path if necessary")
Cc: stable@kernel.org
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20240822023545.1994557-6-libaokun@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/85204
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
2 files changed
