[SRU] [X/B/C/D] [PATCH v2 1/1] openvswitch: fix flow actions reallocation

[Juerg Haefliger]

On Fri,  5 Apr 2019 09:31:53 +0200
Andrea Righi <andrea.righi at canonical.com> wrote:

> BugLink: https://bugs.launchpad.net/bugs/1813244
> 
> 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 at canonical.com>
> Acked-by: Pravin B Shelar <pshelar at ovn.org>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from commit f28cd2af22a0c134e4aa1c64a70f70d815d473fb)
> Signed-off-by: Andrea Righi <andrea.righi at canonical.com>

Clean cherry pick from upstream and indeed seems to fix LP: #1736390. Very nice!

Acked-by: Juerg Haefliger <juergh at canonical.com>


> ---
>  net/openvswitch/flow_netlink.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
> index 691da853bef5..4bdf5e3ac208 100644
> --- a/net/openvswitch/flow_netlink.c
> +++ b/net/openvswitch/flow_netlink.c
> @@ -2306,14 +2306,14 @@ static struct nlattr *reserve_sfa_size(struct sw_flow_actions **sfa,
>  
>  	struct sw_flow_actions *acts;
>  	int new_acts_size;
> -	int req_size = NLA_ALIGN(attr_len);
> +	size_t req_size = NLA_ALIGN(attr_len);
>  	int next_offset = offsetof(struct sw_flow_actions, actions) +
>  					(*sfa)->actions_len;
>  
>  	if (req_size <= (ksize(*sfa) - next_offset))
>  		goto out;
>  
> -	new_acts_size = ksize(*sfa) * 2;
> +	new_acts_size = max(next_offset + req_size, ksize(*sfa) * 2);
>  
>  	if (new_acts_size > MAX_ACTIONS_BUFSIZE) {
>  		if ((MAX_ACTIONS_BUFSIZE - next_offset) < req_size) {

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