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Linux Kernel: Uninitialized File Access When Mounting Directly
CVE-2026-23224
Summary
A bug in the Linux kernel's file system could cause it to access memory that hasn't been properly initialized. This can happen when using a specific option to mount a file system directly. To fix this issue, the kernel developers have made changes to prevent this problem from occurring. If you're using this option, it's recommended to update your kernel to the latest version to ensure you have the fix.
Original title
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_...
Original description
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.
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.
Published: 18 Feb 2026 · Updated: 11 Mar 2026 · First seen: 6 Mar 2026