From: "Eelco Chaudron" <echaudro@redhat.com>
To: "Davide Caratti" <dcaratti@redhat.com>
Cc: "Pravin B Shelar" <pshelar@ovn.org>,
"David S. Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"Sabrina Dubroca" <sd@queasysnail.net>,
netdev@vger.kernel.org
Subject: Re: [PATCH net 1/2] openvswitch: fix stack OOB read while fragmenting IPv4 packets
Date: Wed, 21 Apr 2021 11:27:21 +0200 [thread overview]
Message-ID: <1097839A-30AD-4AE9-859A-4B7C6A3EFA40@redhat.com> (raw)
In-Reply-To: <94839fa9e7995afa6139b4f65c12ac15c1a8dc2f.1618844973.git.dcaratti@redhat.com>
On 19 Apr 2021, at 17:23, Davide Caratti wrote:
> running openvswitch on kernels built with KASAN, it's possible to see
> the
> following splat while testing fragmentation of IPv4 packets:
<SNIP>
> for IPv4 packets, ovs_fragment() uses a temporary struct dst_entry.
> Then,
> in the following call graph:
>
> ip_do_fragment()
> ip_skb_dst_mtu()
> ip_dst_mtu_maybe_forward()
> ip_mtu_locked()
>
> the pointer to struct dst_entry is used as pointer to struct rtable:
> this
> turns the access to struct members like rt_mtu_locked into an OOB read
> in
> the stack. Fix this changing the temporary variable used for IPv4
> packets
> in ovs_fragment(), similarly to what is done for IPv6 few lines below.
>
> Fixes: d52e5a7e7ca4 ("ipv4: lock mtu in fnhe when received PMTU <
> net.ipv4.route.min_pmt")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>
The fix looks good to me, however isn’t the real root cause
ip_mtu_locked() who casts struct dst_entry to struct rtable (not even
using container_of())?
I do not know details in this area of the code, so maybe it’s just
fine to always assume dst_entry is part of a rtable struct, as I see
other core functions do the same
ipv4_neigh_lookup()/ipv4_confirm_neigh().
Acked-by: Eelco Chaudron <echaudro@redhat.com>
next prev parent reply other threads:[~2021-04-21 9:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 15:22 [PATCH net 0/2] fix stack OOB read while fragmenting IPv4 packets Davide Caratti
2021-04-19 15:23 ` [PATCH net 1/2] openvswitch: " Davide Caratti
2021-04-21 9:27 ` Eelco Chaudron [this message]
2021-04-21 15:05 ` Davide Caratti
2021-04-22 9:17 ` Eelco Chaudron
2021-04-19 15:23 ` [PATCH net 2/2] net/sched: sch_frag: " Davide Caratti
2021-04-19 17:38 ` Marcelo Ricardo Leitner
2021-04-19 18:46 ` Cong Wang
2021-04-20 8:59 ` Davide Caratti
2021-04-20 19:25 ` Cong Wang
2021-04-20 19:27 ` Cong Wang
2021-04-23 12:11 ` [PATCH net 0/2] " Davide Caratti
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