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linux/fs/erofs
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Chao Yu ae38582684 erofs: fix UAF issue for file-backed mounts w/ directio option 
commit 1caf50ce4a upstream.

[    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.

Cc: stable@kernel.org
Fixes: fb17675026 ("erofs: add file-backed mount support")
Fixes: 6422cde1b0 ("erofs: use buffered I/O for file-backed mounts by default")
Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-02-16 10:18:45 +01:00
..
compress.h erofs: avoid refcounting short-lived pages 2024-07-11 15:14:26 +08:00
data.c erofs: fix to add missing tracepoint in erofs_readahead() 2025-07-17 18:37:18 +02:00
decompressor.c erofs: address D-cache aliasing 2025-07-17 18:37:15 +02:00
decompressor_deflate.c erofs: tidy up stream decompressors 2024-07-09 19:04:41 +08:00
decompressor_lzma.c erofs: convert comma to semicolon 2024-07-26 18:48:12 +08:00
decompressor_zstd.c erofs: avoid infinite loop due to incomplete zstd-compressed data 2025-11-24 10:35:49 +01:00
dir.c erofs: simplify readdir operation 2024-08-19 11:06:20 +08:00
erofs_fs.h erofs: restrict pcluster size limitations 2024-09-12 23:00:09 +08:00
fileio.c erofs: fix UAF issue for file-backed mounts w/ directio option 2026-02-16 10:18:45 +01:00
fscache.c erofs: reference struct erofs_device_info for erofs_map_dev 2024-12-27 14:02:00 +01:00
inode.c erofs: reject inodes with negative i_size 2024-09-12 23:00:09 +08:00
internal.h erofs: fix large fragment handling 2025-08-01 09:48:45 +01:00
Kconfig erofs: mark experimental fscache backend deprecated 2024-09-10 15:27:11 +08:00
Makefile erofs: support unencoded inodes for fileio 2024-09-10 15:26:36 +08:00
namei.c erofs_buf: store address_space instead of inode 2024-04-25 00:57:14 -04:00
super.c erofs: fix file-backed mounts no longer working on EROFS partitions 2026-01-17 16:31:25 +01:00
sysfs.c erofs: clean up erofs_register_sysfs() 2024-09-10 00:46:34 +08:00
xattr.c add a string-to-qstr constructor 2025-07-10 16:05:08 +02:00
xattr.h erofs: move erofs_xattr_handlers and xattr_handler_map to .rodata 2023-10-09 16:24:17 +02:00
zdata.c erofs: fix unexpected EIO under memory pressure 2026-01-08 10:14:56 +01:00
zmap.c erofs: fix large fragment handling 2025-08-01 09:48:45 +01:00
zutil.c erofs: fix rare pcluster memory leak after unmounting 2025-07-17 18:37:23 +02:00