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Date: Wed, 17 Mar 2021 18:39:14 +0300
From: Evgenii Shatokhin <>
To: Salvatore Bonaccorso <>
Subject: Re: CVE-2021-20219 Linux kernel: improper
 synchronization in flush_to_ldisc() can lead to DoS

On 17.03.2021 18:29, Salvatore Bonaccorso wrote:
> Hi Rohit,
> On Wed, Mar 17, 2021 at 04:17:05PM +0100, Greg KH wrote:
>> On Wed, Mar 17, 2021 at 07:45:59PM +0530, Rohit Keshri wrote:
>>> Hello Team,
>>> A denial of service vulnerability was found in n_tty_receive_char_special
>>> in drivers/tty/n_tty.c of the Linux kernel.  In this flaw a local attacker
>>> with a normal user privilege could delay the loop (due to a changing
>>> ldata->read_head, and a missing sanity check) and cause a threat to the
>>> system availability.
>>> 'CVE-2021-20219' was assigned by Red Hat.
>>> Acknowledgements: Evgenii Shatokhin (Virtuozzo Research LLC)
>> Really?  Not the tools or people that reported this issue and fixed it
>> in the community back in 2018?
> Can you clarify, would 3d63b7e4ae0d ("n_tty: Fix stall at
> n_tty_receive_char_special().") be the upstream fix you are referring
> to for it?

Sorry for jumping in.

Yes, this is the original fix, but the issue I reported is specific to 
RHEL 7: their backport of that fix was incomplete.

> Regards,
> Salvatore
> .



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