2018-09-25 09:31:01

by Kirill Tkhai

Subject: [PATCH] fuse: Fix use-after-free in fuse_dev_do_read()

We may pick freed req in this way:

[cpu0] [cpu1]
fuse_dev_do_read() fuse_dev_do_write()
list_move_tail(&req->list, &fpq->processing); ...
spin_unlock(&fpq->lock); ...
... request_end(fc, req);
... fuse_put_request(fc, req);
if (test_bit(FR_INTERRUPTED, &req->flags))
queue_interrupt(fiq, req);

Fix that by keeping req alive till we finish all manipulations.

Reported-by: [email protected]
Signed-off-by: Kirill Tkhai <[email protected]>
---
fs/fuse/dev.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 11ea2c4a38ab..675caed3e655 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1311,12 +1311,14 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
goto out_end;
}
list_move_tail(&req->list, &fpq->processing);
+ __fuse_get_request(req);
spin_unlock(&fpq->lock);
set_bit(FR_SENT, &req->flags);
/* matches barrier in request_wait_answer() */
smp_mb__after_atomic();
if (test_bit(FR_INTERRUPTED, &req->flags))
queue_interrupt(fiq, req);
+ fuse_put_request(fc, req);

return reqsize;

2018-10-01 09:26:15

by Miklos Szeredi

Subject: Re: [PATCH] fuse: Fix use-after-free in fuse_dev_do_read()

On Tue, Sep 25, 2018 at 11:28 AM, Kirill Tkhai <[email protected]> wrote:
> We may pick freed req in this way:
>
> [cpu0] [cpu1]
> fuse_dev_do_read() fuse_dev_do_write()
> list_move_tail(&req->list, &fpq->processing); ...
> spin_unlock(&fpq->lock); ...
> ... request_end(fc, req);
> ... fuse_put_request(fc, req);
> if (test_bit(FR_INTERRUPTED, &req->flags))
> queue_interrupt(fiq, req);
>
> Fix that by keeping req alive till we finish all manipulations.
>
> Reported-by: [email protected]
> Signed-off-by: Kirill Tkhai <[email protected]>

Applied.

Thanks,
Miklos