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Date: Sat, 30 Jan 2021 16:46:30 +0800
From: butt3rflyh4ck <>
Subject: Re: Linux kernel: linux-block: nbd: use-after-free Read in nbd_queue_rq

the patch for this issue in upstream:


On Fri, Jan 29, 2021 at 2:10 AM butt3rflyh4ck <>

> Hi, I reported a use-after-free Read bug in ndb_queue_rq() in
> drivers/block/nbd.c and reproduced in linux-5.11.0-rc4+ too.
> Root Cause:
> There is a race condition in nbd ioctl.
> NBD_SET_SIZE_BLOCKS ioctl will call nbd_size_set(), it will change the
> block size.
> NBD_SET_SOCK ioctl will call nbd_add_socket() and it will invoke
> krealloc() to update a block, free and realloc a new one.
> But nbd_queue_rq() is in runtime. and calls nbd_handle_cmd(), there
> will use config->sock. there accesses to config->socks without any locking.
> Patch for this issue:
> CVE assigned:
> not assigned.
> Timeline:
> *2021/1/25  - Vulnerability reported to
> *2020/1/26  - Vulnerability confirmed and patched.
> *2020/1/28 - Vulnerability reported to
> *2021/1/29 - Opened on
> Credit:
> This issue was discovered by the ADLab of venustech.
> Regards,
>  butt3rflyh4ck.

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