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Date:   Thu, 28 Mar 2019 17:16:40 -0700 (PDT)
Message-Id: <20190328.171640.1161931383487396254.davem@davemloft.net>
To:     andrea.righi@canonical.com
Cc:     pshelar@ovn.org, netdev@vger.kernel.org, dev@openvswitch.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] openvswitch: fix flow actions reallocation
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20190328063600.GC16096@xps-13>
References: <20190328063600.GC16096@xps-13>
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From: Andrea Righi <andrea.righi@canonical.com>
Date: Thu, 28 Mar 2019 07:36:00 +0100

> The flow action buffer can be resized if it's not big enough to contain
> all the requested flow actions. However, this resize doesn't take into
> account the new requested size, the buffer is only increased by a factor
> of 2x. This might be not enough to contain the new data, causing a
> buffer overflow, for example:
> 
> [   42.044472] =============================================================================
> [   42.045608] BUG kmalloc-96 (Not tainted): Redzone overwritten
> [   42.046415] -----------------------------------------------------------------------------
> 
> [   42.047715] Disabling lock debugging due to kernel taint
> [   42.047716] INFO: 0x8bf2c4a5-0x720c0928. First byte 0x0 instead of 0xcc
> [   42.048677] INFO: Slab 0xbc6d2040 objects=29 used=18 fp=0xdc07dec4 flags=0x2808101
> [   42.049743] INFO: Object 0xd53a3464 @offset=2528 fp=0xccdcdebb
> 
> [   42.050747] Redzone 76f1b237: cc cc cc cc cc cc cc cc                          ........
> [   42.051839] Object d53a3464: 6b 6b 6b 6b 6b 6b 6b 6b 0c 00 00 00 6c 00 00 00  kkkkkkkk....l...
> [   42.053015] Object f49a30cc: 6c 00 0c 00 00 00 00 00 00 00 00 03 78 a3 15 f6  l...........x...
> [   42.054203] Object acfe4220: 20 00 02 00 ff ff ff ff 00 00 00 00 00 00 00 00   ...............
> [   42.055370] Object 21024e91: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [   42.056541] Object 070e04c3: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [   42.057797] Object 948a777a: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> [   42.059061] Redzone 8bf2c4a5: 00 00 00 00                                      ....
> [   42.060189] Padding a681b46e: 5a 5a 5a 5a 5a 5a 5a 5a                          ZZZZZZZZ
> 
> Fix by making sure the new buffer is properly resized to contain all the
> requested data.
> 
> BugLink: https://bugs.launchpad.net/bugs/1813244
> Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

Applied and queued up for -stable.

Althought next time I want to see a proper Fixes: tag.