From: Daniel Borkmann <dborkman@redhat.com>
To: davem@davemloft.net
Cc: netdev@vger.kernel.org, Benjamin Poirier <bpoirier@suse.de>,
Steffen Klassert <steffen.klassert@secunet.com>
Subject: [PATCH net] net: esp{4,6}: fix potential MTU calculation overflows
Date: Mon, 5 Aug 2013 12:49:35 +0200 [thread overview]
Message-ID: <1375699775-13769-1-git-send-email-dborkman@redhat.com> (raw)
Commit 91657eafb ("xfrm: take net hdr len into account for esp payload
size calculation") introduced a possible interger overflow in
esp{4,6}_get_mtu() handlers in case of x->props.mode equals
XFRM_MODE_TUNNEL. Thus, the following expression will overflow
unsigned int net_adj;
...
<case ipv{4,6} XFRM_MODE_TUNNEL>
net_adj = 0;
...
return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
net_adj) & ~(align - 1)) + (net_adj - 2);
where (net_adj - 2) would be evaluated as <foo> + (0 - 2) in an unsigned
context. Fix it by simply removing brackets as those operations here
do not need to have special precedence.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Benjamin Poirier <bpoirier@suse.de>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
---
Note: only compile tested, maybe Benjamin can comment on why he added
brackets around this expression. *If* this is valid (which I do
not think), then this needs at least a big comment explaining so.
net/ipv4/esp4.c | 2 +-
net/ipv6/esp6.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index ab3d814..109ee89 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -477,7 +477,7 @@ static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
}
return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
- net_adj) & ~(align - 1)) + (net_adj - 2);
+ net_adj) & ~(align - 1)) + net_adj - 2;
}
static void esp4_err(struct sk_buff *skb, u32 info)
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 40ffd72..aeac0dc 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -425,7 +425,7 @@ static u32 esp6_get_mtu(struct xfrm_state *x, int mtu)
net_adj = 0;
return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
- net_adj) & ~(align - 1)) + (net_adj - 2);
+ net_adj) & ~(align - 1)) + net_adj - 2;
}
static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
--
1.7.11.7
next reply other threads:[~2013-08-05 10:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-05 10:49 Daniel Borkmann [this message]
2013-08-05 14:38 ` [PATCH net] net: esp{4,6}: fix potential MTU calculation overflows Benjamin Poirier
2013-08-05 19:27 ` David Miller
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