CVE-2024-49884 HIGH

In the Linux kernel, the following vulnerability has been resolved: ext4: fix slab-use-after-free in ext4_split_extent_at() We hit the following use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: <TASK> kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ================================================================== The flow of issue triggering is as follows: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!! So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path. In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates.

Additional Descriptions (1)

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ext4: corrección de slab-use-after-free en ext4_split_extent_at() Nos topamos con el siguiente use after free: ====================================================================== ERROR: KASAN: slab-use-after-free en ext4_split_extent_at+0xba8/0xcc0 Lectura de tamaño 2 en la dirección ffff88810548ed08 por la tarea kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 No contaminado 6.9.0-dirty #724 Seguimiento de llamadas: kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Asignado por la tarea 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Liberado por la tarea 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ==================================================================== El flujo de activación del problema es el siguiente: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // devuelve -ENOMEM o -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. Si err es -ENOMEM: ext4_ext_dirty(path + path-&gt;p_depth) // ¡¡¡path use after free!!! b. Si err es -EIO y tenemos EXT_DEBUG definido: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // ¡¡¡La ruta también es use after free!!! Por lo tanto, cuando intente poner a cero o corregir la longitud de la extensión, llame a ext4_find_extent() para actualizar la ruta. Además, usamos *ppath directamente como una entrada de ext4_ext_show_leaf() para evitar un posible use after free cuando se define EXT_DEBUG y para evitar actualizaciones de ruta innecesarias.

Source	Type	Description
[email protected]	Primary	en CWE-416

• https://git.kernel.org/stable/c/393a46f60ea4f249dc9d496d4eb2d542f5e11ade
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/448100a29395b0c8b4c42967155849fe0fbe808f
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/5d949ea75bb529ea6342e83465938a3b0ac51238
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/8fe117790b37c84c651e2bad9efc0e7fda73c0e3
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/915ac3630488af0ca194dc63b86d99802b4f6e18
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/a5401d4c3e2a3d25643c567d26e6de327774a2c9
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/c26ab35702f8cd0cdc78f96aa5856bfb77be798f
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/cafcc1bd62934547c76abf46c6d0d54f135006fe
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://git.kernel.org/stable/c/e52f933598b781d291b9297e39c463536da0e185
  Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  Patch
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
  Source: af854a3a-2127-422b-91ae-364da2661108
  Broken Link
• https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html
  Source: af854a3a-2127-422b-91ae-364da2661108
  Mailing List Third Party Advisory