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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, ...); ...
spin_unlock(&fpq->lock); ...
... request_end(fc, req);
... fuse_put_request(fc, req);
if (test_bit(FR_INTERRUPTED, ...))
queue_interrupt(fiq, req);
Fix that by keeping req alive until we finish all manipulations.
Reported-by: syzbot+4e975615ca01f2277bdd@syzkaller.appspotmail.com
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 46c34a348b
("fuse: no fc->lock for pqueue parts")
Cc: <stable@vger.kernel.org> # v4.2
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1 changed files with 2 additions and 0 deletions
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@ -1311,12 +1311,14 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
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goto out_end;
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}
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list_move_tail(&req->list, &fpq->processing);
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__fuse_get_request(req);
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spin_unlock(&fpq->lock);
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set_bit(FR_SENT, &req->flags);
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/* matches barrier in request_wait_answer() */
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smp_mb__after_atomic();
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if (test_bit(FR_INTERRUPTED, &req->flags))
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queue_interrupt(fiq, req);
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fuse_put_request(fc, req);
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return reqsize;
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