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Subject[PATCH 1/7] staging: erofs: fix use-after-free of on-stack `z_erofs_vle_unzip_io'
Date
The root cause is the race as follows:
Thread #0 Thread #1

z_erofs_vle_unzip_kickoff z_erofs_submit_and_unzip

struct z_erofs_vle_unzip_io io[]
atomic_add_return()
wait_event()
[end of function]
wake_up()

Fix it by taking the waitqueue lock between atomic_add_return and
wake_up to close such the race.

kernel message:

Unable to handle kernel paging request at virtual address 97f7052caa1303dc
...
Workqueue: kverityd verity_work
task: ffffffe32bcb8000 task.stack: ffffffe3298a0000
PC is at __wake_up_common+0x48/0xa8
LR is at __wake_up+0x3c/0x58
...
Call trace:
...
[<ffffff94a08ff648>] __wake_up_common+0x48/0xa8
[<ffffff94a08ff8b8>] __wake_up+0x3c/0x58
[<ffffff94a0c11b60>] z_erofs_vle_unzip_kickoff+0x40/0x64
[<ffffff94a0c118e4>] z_erofs_vle_read_endio+0x94/0x134
[<ffffff94a0c83c9c>] bio_endio+0xe4/0xf8
[<ffffff94a1076540>] dec_pending+0x134/0x32c
[<ffffff94a1076f28>] clone_endio+0x90/0xf4
[<ffffff94a0c83c9c>] bio_endio+0xe4/0xf8
[<ffffff94a1095024>] verity_work+0x210/0x368
[<ffffff94a08c4150>] process_one_work+0x188/0x4b4
[<ffffff94a08c45bc>] worker_thread+0x140/0x458
[<ffffff94a08cad48>] kthread+0xec/0x108
[<ffffff94a0883ab4>] ret_from_fork+0x10/0x1c
Code: d1006273 54000260 f9400804 b9400019 (b85fc081)
---[ end trace be9dde154f677cd1 ]---

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
drivers/staging/erofs/unzip_vle.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
index f5d088fdf7f2..4404ea6fb9e4 100644
--- a/drivers/staging/erofs/unzip_vle.c
+++ b/drivers/staging/erofs/unzip_vle.c
@@ -744,13 +744,18 @@ static void z_erofs_vle_unzip_kickoff(void *ptr, int bios)
struct z_erofs_vle_unzip_io *io = tagptr_unfold_ptr(t);
bool background = tagptr_unfold_tags(t);

- if (atomic_add_return(bios, &io->pending_bios))
+ if (!background) {
+ unsigned long flags;
+
+ spin_lock_irqsave(&io->u.wait.lock, flags);
+ if (!atomic_add_return(bios, &io->pending_bios))
+ wake_up_locked(&io->u.wait);
+ spin_unlock_irqrestore(&io->u.wait.lock, flags);
return;
+ }

- if (background)
+ if (!atomic_add_return(bios, &io->pending_bios))
queue_work(z_erofs_workqueue, &io->u.work);
- else
- wake_up(&io->u.wait);
}

static inline void z_erofs_vle_read_endio(struct bio *bio)
--
2.14.4
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