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| author | Gao Xiang <hsiangkao@linux.alibaba.com> | 2026-05-22 16:27:16 +0800 |
|---|---|---|
| committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2026-05-29 12:32:56 +0800 |
| commit | 1aee05e814d292064bf5fa15733741040cdc48ba (patch) | |
| tree | a834d3417971c32b0a394db574d0df1496a8c2c9 | |
| parent | e7ae89a0c97ce2b68b0983cd01eda67cf373517d (diff) | |
| download | linux-stable-1aee05e814d292064bf5fa15733741040cdc48ba.tar.gz linux-stable-1aee05e814d292064bf5fa15733741040cdc48ba.zip | |
erofs: fix use-after-free on sbi->sync_decompress
z_erofs_decompress_kickoff() can race with filesystem unmount, causing
a use-after-free on sbi->sync_decompress.
When I/O completes, z_erofs_endio() calls z_erofs_decompress_kickoff()
to queue z_erofs_decompressqueue_work() asynchronously. Then, after all
folios are unlocked, unmount workflow can proceed and sbi will be freed
before accessing to sbi->sync_decompress.
Thread (unmount) I/O completion kworker
queue_work
z_erofs_decompressqueue_work
(all folios are unlocked)
cleanup_mnt
..
erofs_kill_sb
erofs_sb_free
kfree(sbi)
access sbi->sync_decompress // UAF!!
Fixes: 40452ffca3c1 ("erofs: add sysfs node to control sync decompression strategy")
Reported-by: syzbot+52bae5c495dbe261a0bc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=52bae5c495dbe261a0bc
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Jianan Huang <jnhuang95@gmail.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
| -rw-r--r-- | fs/erofs/zdata.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 27ab7bd844ec..c6240dccbb0f 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -1455,6 +1455,9 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io, if (atomic_add_return(bios, &io->pending_bios)) return; if (z_erofs_in_atomic()) { + /* See `sync_decompress` in sysfs-fs-erofs for more details */ + if (sbi->sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) + sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON; #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD struct kthread_worker *worker; @@ -1471,9 +1474,6 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io, #else queue_work(z_erofs_workqueue, &io->u.work); #endif - /* See `sync_decompress` in sysfs-fs-erofs for more details */ - if (sbi->sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO) - sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON; return; } gfp_flag = memalloc_noio_save(); |