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Date: Wed, 17 Mar 2021 12:40:41 +0000
From: John Haxby <john.haxby@...cle.com>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: Re: Use After Free and Double Free bugs in Linux
Kernel mainline
This one isn't a security bug:
> On 17 Mar 2021, at 11:53, lyl2019@...l.ustc.edu.cn wrote:
>
> Bug2: nvme/rdma: Fix a use after free in nvmet_rdma_write_data_done
> Commit Url: https://github.com/torvalds/linux/commit/abec6561fc4e0fbb19591a0b35676d8c783b5493
>
> In nvmet_rdma_write_data_done, rsp is recoverd by wc->wr_cqe
> and freed by nvmet_rdma_release_rsp(). But after that, pr_info()
> used the freed chunk's member object and could leak the freed
> chunk address with wc->wr_cqe by computing the offset.
>
> drivers/nvme/target/rdma.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
> index 06b6b742bb21..6c1f3ab7649c 100644
> --- a/drivers/nvme/target/rdma.c
> +++ b/drivers/nvme/target/rdma.c
> @@ -802,9 +802,8 @@ static void nvmet_rdma_write_data_done(struct ib_cq *cq, struct ib_wc *wc)
> nvmet_req_uninit(&rsp->req);
> nvmet_rdma_release_rsp(rsp);
> if (wc->status != IB_WC_WR_FLUSH_ERR) {
> - pr_info("RDMA WRITE for CQE 0x%p failed with status %s (%d).\n",
> - wc->wr_cqe, ib_wc_status_msg(wc->status),
> - wc->status);
> + pr_info("RDMA WRITE for CQE failed with status %s (%d).\n",
> + ib_wc_status_msg(wc->status), wc->status);
> nvmet_rdma_error_comp(queue);
> }
> return;
Commit ad67b74d2469 ("printk: hash addresses printed with %p") back in 2017 made '%p' a non-security issue. That commit noted that there were approximately 14,000 places in the kernel where there was an address printed with %p. Rather than 14,000 CVEs :) this was fixed once and once only by that commit.
That's not to say that this "0x%p" doesn't have a problem: for a start you don't need the "0x" because %p prints one anyway. That point is moot, though, because no one objected to just removing the pointer. The commit message is wrong though: it doesn't leak an address.
jch
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