netdev - Re: [PATCH net v2] net/tls: fix sk_msg trim on fallback to copy mode

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Message-Id: <20191105.180829.228337395055155315.davem@davemloft.net>
Date:   Tue, 05 Nov 2019 18:08:29 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     jakub.kicinski@...ronome.com
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        borisp@...lanox.com, aviadye@...lanox.com,
        john.fastabend@...il.com, daniel@...earbox.net,
        syzbot+f8495bff23a879a6d0bd@...kaller.appspotmail.com,
        syzbot+6f50c99e8f6194bf363f@...kaller.appspotmail.com,
        ebiggers@...nel.org, herbert@...dor.apana.org.au,
        glider@...gle.com, linux-crypto@...r.kernel.org
Subject: Re: [PATCH net v2] net/tls: fix sk_msg trim on fallback to copy
 mode

From: Jakub Kicinski <jakub.kicinski@...ronome.com>
Date: Mon,  4 Nov 2019 15:36:57 -0800

> sk_msg_trim() tries to only update curr pointer if it falls into
> the trimmed region. The logic, however, does not take into the
> account pointer wrapping that sk_msg_iter_var_prev() does nor
> (as John points out) the fact that msg->sg is a ring buffer.
> 
> This means that when the message was trimmed completely, the new
> curr pointer would have the value of MAX_MSG_FRAGS - 1, which is
> neither smaller than any other value, nor would it actually be
> correct.
> 
> Special case the trimming to 0 length a little bit and rework
> the comparison between curr and end to take into account wrapping.
> 
> This bug caused the TLS code to not copy all of the message, if
> zero copy filled in fewer sg entries than memcopy would need.
> 
> Big thanks to Alexander Potapenko for the non-KMSAN reproducer.
> 
> v2:
>  - take into account that msg->sg is a ring buffer (John).
> 
> Link: https://lore.kernel.org/netdev/20191030160542.30295-1-jakub.kicinski@netronome.com/ (v1)
> 
> Fixes: d829e9c4112b ("tls: convert to generic sk_msg interface")
> Reported-by: syzbot+f8495bff23a879a6d0bd@...kaller.appspotmail.com
> Reported-by: syzbot+6f50c99e8f6194bf363f@...kaller.appspotmail.com
> Co-developed-by: John Fastabend <john.fastabend@...il.com>
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Applied and queued up for -stable, thanks Jakub.