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io_uring: fix use-after-free of shadow_req 

There is a potential dangling pointer problem. we never clean
shadow_req, if there are multiple link lists in this series of
sqes, then the shadow_req will not reallocate, and continue to
use the last one. but in the previous, his memory has been
released, thus forming a dangling pointer. let's clean up him
and make sure that every new link list can reapply for a new
shadow_req.

Fixes: 4fe2c96315 ("io_uring: add support for link with drain")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jackie Liu 2019-09-18 10:37:53 +08:00 committed by Jens Axboe
parent 954dab193d
commit 5f5ad9ced3
1 changed files with 2 additions and 0 deletions
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2
fs/io_uring.c
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@ -2357,6 +2357,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
io_queue_link_head(ctx, link, &link->submit, shadow_req,
true);
link = NULL;
shadow_req = NULL;
}
prev_was_link = (sqes[i].sqe->flags & IOSQE_IO_LINK) != 0;
@ -2543,6 +2544,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
io_queue_link_head(ctx, link, &link->submit, shadow_req,
force_nonblock);
link = NULL;
shadow_req = NULL;
}
prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0;