From: David Miller <davem@davemloft.net>
To: vinay.yadav@chelsio.com
Cc: netdev@vger.kernel.org, kuba@kernel.org, secdev@chelsio.com
Subject: Re: [PATCH net-next,v2] net/tls: fix race condition causing kernel panic
Date: Mon, 25 May 2020 17:42:41 -0700 (PDT) [thread overview]
Message-ID: <20200525.174241.85970384865891191.davem@davemloft.net> (raw)
In-Reply-To: <20200522201031.32516-1-vinay.yadav@chelsio.com>
From: Vinay Kumar Yadav <vinay.yadav@chelsio.com>
Date: Sat, 23 May 2020 01:40:31 +0530
> tls_sw_recvmsg() and tls_decrypt_done() can be run concurrently.
> // tls_sw_recvmsg()
> if (atomic_read(&ctx->decrypt_pending))
> crypto_wait_req(-EINPROGRESS, &ctx->async_wait);
> else
> reinit_completion(&ctx->async_wait.completion);
>
> //tls_decrypt_done()
> pending = atomic_dec_return(&ctx->decrypt_pending);
>
> if (!pending && READ_ONCE(ctx->async_notify))
> complete(&ctx->async_wait.completion);
>
> Consider the scenario tls_decrypt_done() is about to run complete()
>
> if (!pending && READ_ONCE(ctx->async_notify))
>
> and tls_sw_recvmsg() reads decrypt_pending == 0, does reinit_completion(),
> then tls_decrypt_done() runs complete(). This sequence of execution
> results in wrong completion. Consequently, for next decrypt request,
> it will not wait for completion, eventually on connection close, crypto
> resources freed, there is no way to handle pending decrypt response.
>
> This race condition can be avoided by having atomic_read() mutually
> exclusive with atomic_dec_return(),complete().Intoduced spin lock to
> ensure the mutual exclution.
>
> Addressed similar problem in tx direction.
>
> v1->v2:
> - More readable commit message.
> - Corrected the lock to fix new race scenario.
> - Removed barrier which is not needed now.
>
> Signed-off-by: Vinay Kumar Yadav <vinay.yadav@chelsio.com>
Applied to 'net' as this is a bug fix, with Fixes tag from Jakub added,
and queued up for -stable.
Thanks.
prev parent reply other threads:[~2020-05-26 0:42 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-22 20:10 [PATCH net-next,v2] net/tls: fix race condition causing kernel panic Vinay Kumar Yadav
2020-05-25 20:25 ` Jakub Kicinski
2020-05-26 0:42 ` David Miller [this message]
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