On Wed, Mar 27, 2019 at 3:11 PM Andrea Righi <andrea.ri...@canonical.com> wrote: > > 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.ri...@canonical.com>
This must be rare combination of action that trigger this case. > --- > 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..e6f789badaa3 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(req_size, ksize(*sfa) * 2); > Don't we need to compare current_action_size+req_size and current_action_size*2 here ? > if (new_acts_size > MAX_ACTIONS_BUFSIZE) { > if ((MAX_ACTIONS_BUFSIZE - next_offset) < req_size) { > -- > 2.19.1 > _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev