CVE-2026-23224

In the Linux kernel, the following vulnerability has been resolved:

erofs: fix UAF issue for file-backed mounts w/ directio option

[ 9.269940][ T3222] Call trace: [ 9.269948][ T3222] ext4_file_read_iter+0xac/0x108 [ 9.269979][ T3222] vfs_iocb_iter_read+0xac/0x198 [ 9.269993][ T3222] erofs_fileio_rq_submit+0x12c/0x180 [ 9.270008][ T3222] erofs_fileio_submit_bio+0x14/0x24 [ 9.270030][ T3222] z_erofs_runqueue+0x834/0x8ac [ 9.270054][ T3222] z_erofs_read_folio+0x120/0x220 [ 9.270083][ T3222] filemap_read_folio+0x60/0x120 [ 9.270102][ T3222] filemap_fault+0xcac/0x1060 [ 9.270119][ T3222] do_pte_missing+0x2d8/0x1554 [ 9.270131][ T3222] handle_mm_fault+0x5ec/0x70c [ 9.270142][ T3222] do_page_fault+0x178/0x88c [ 9.270167][ T3222] do_translation_fault+0x38/0x54 [ 9.270183][ T3222] do_mem_abort+0x54/0xac [ 9.270208][ T3222] el0_da+0x44/0x7c [ 9.270227][ T3222] el0t_64_sync_handler+0x5c/0xf4 [ 9.270253][ T3222] el0t_64_sync+0x1bc/0x1c0

EROFS may encounter above panic when enabling file-backed mount w/ directio mount option, the root cause is it may suffer UAF in below race condition:

• z_erofs_read_folio wq s_dio_done_wq
• z_erofs_runqueue
• erofs_fileio_submit_bio
• erofs_fileio_rq_submit - vfs_iocb_iter_read
  • ext4_file_read_iter
  • ext4_dio_read_iter
  • iomap_dio_rw : bio was submitted and return -EIOCBQUEUED - dio_aio_complete_work - dio_complete - dio->iocb->ki_complete (erofs_fileio_ki_complete()) - kfree(rq) : it frees iocb, iocb.ki_filp can be UAF in file_accessed().
  • file_accessed : access NULL file point

Introduce a reference count in struct erofs_fileio_rq, and initialize it as two, both erofs_fileio_ki_complete() and erofs_fileio_rq_submit() will decrease reference count, the last one decreasing the reference count to zero will free rq.

Affected Software

References

• https://git.kernel.org/stable/c/ae385826840a3c8e09bf38cac90adcd690716f57
• https://git.kernel.org/stable/c/b2ee5e4d5446babd23ff7beb4e636be0fb3ea5aa
• https://git.kernel.org/stable/c/d741534302f71c511eb0bb670b92eaa7df4a0aec