Re: PROBLEM: System call 'sendmsg' of process ospfd (quagga) causes kernel oops
From: Eric Dumazet <hidden>
Date: 2011-10-18 12:55:44
Also in:
lkml
Subsystem:
networking drivers, networking [general], the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Le mardi 18 octobre 2011 à 13:49 +0200, Herbert Xu a écrit :
On Tue, Oct 18, 2011 at 01:37:58PM +0200, Eric Dumazet wrote:quoted
In the bug we try to fix, we have : skb = sock_alloc_send_skb(sk, ... + LL_ALLOCATED_SPACE(rt->dst.dev) ... < increase of dev->needed_headroom by another cpu/task > skb_reserve(skb, LL_RESERVED_SPACE(rt->dst.dev));OK, in that case one fix would be to replace LL_ALLOCATED_SPACE with its two constiuents so that they may be stored in local variables for later use. hlen = LL_HEADROOM(skb); tlen = LL_TAILROOM(skb); skb_alloc_send_skb(sk, ... + LL_ALIGN(hlen + tlen)); skb_reserve(skb, LL_ALIGN(hlen)); Cheers,
I am ok by this way, but we might hit another similar problem elsewhere. (igmp.c ip6_output, ...) We effectively want to remove LL_ALLOCATED_SPACE() usage and obfuscate code... [PATCH] raw: allow dev->needed_headroom dynamic change It seems ip_gre is able to change dev->needed_headroom on the fly. It triggers a BUG in raw_sendmsg() skb = sock_alloc_send_skb(sk, ... + LL_ALLOCATED_SPACE(rt->dst.dev) < another cpu change dev->needed_headromm (making it bigger) ... skb_reserve(skb, LL_RESERVED_SPACE(rt->dst.dev)); We end with LL_RESERVED_SPACE() being bigger than LL_ALLOCATED_SPACE() -> we crash later because skb head is exhausted. Bug introduced in commit 243aad83 in 2.6.34 (ip_gre: include route header_len in max_headroom calculation) Reported-by: Reported-by: Elmar Vonlanthen <redacted> Signed-off-by: Eric Dumazet <redacted> CC: Timo Teräs <redacted> CC: Herbert Xu <herbert@gondor.apana.org.au> --- include/linux/netdevice.h | 10 +++++++--- net/ipv4/raw.c | 9 +++++++-- net/ipv6/raw.c | 9 +++++++-- 3 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index ddee79b..dba2399 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -276,12 +276,16 @@ struct hh_cache { * LL_ALLOCATED_SPACE also takes into account the tailroom the device * may need. */ +#define LL_ALIGN(__len) (((__len)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD) + #define LL_RESERVED_SPACE(dev) \ - ((((dev)->hard_header_len+(dev)->needed_headroom)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD) + LL_ALIGN((dev)->hard_header_len + (dev)->needed_headroom)) + #define LL_RESERVED_SPACE_EXTRA(dev,extra) \ - ((((dev)->hard_header_len+(dev)->needed_headroom+(extra))&~(HH_DATA_MOD - 1)) + HH_DATA_MOD) + LL_ALIGN((dev)->hard_header_len + (dev)->needed_headroom + (extra)) + #define LL_ALLOCATED_SPACE(dev) \ - ((((dev)->hard_header_len+(dev)->needed_headroom+(dev)->needed_tailroom)&~(HH_DATA_MOD - 1)) + HH_DATA_MOD) + LL_ALIGN((dev)->hard_header_len + (dev)->needed_headroom + (dev)->needed_tailroom) struct header_ops { int (*create) (struct sk_buff *skb, struct net_device *dev,
diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 61714bd..4ed4eda 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c@@ -326,6 +326,9 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4, unsigned int iphlen; int err; struct rtable *rt = *rtp; + unsigned int hard_header_len = rt->dst.dev->hard_header_len; + unsigned int needed_headroom = rt->dst.dev->needed_headroom; + unsigned int needed_tailroom = rt->dst.dev->needed_tailroom; if (length > rt->dst.dev->mtu) { ip_local_error(sk, EMSGSIZE, fl4->daddr, inet->inet_dport,
@@ -336,11 +339,13 @@ static int raw_send_hdrinc(struct sock *sk, struct flowi4 *fl4, goto out; skb = sock_alloc_send_skb(sk, - length + LL_ALLOCATED_SPACE(rt->dst.dev) + 15, + length + LL_ALIGN(hard_header_len + + needed_headroom + + needed_tailroom) + 15, flags & MSG_DONTWAIT, &err); if (skb == NULL) goto error; - skb_reserve(skb, LL_RESERVED_SPACE(rt->dst.dev)); + skb_reserve(skb, LL_ALIGN(hard_header_len + needed_headroom)); skb->priority = sk->sk_priority; skb->mark = sk->sk_mark;
diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index 343852e..eb0a797 100644
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c@@ -610,6 +610,9 @@ static int rawv6_send_hdrinc(struct sock *sk, void *from, int length, struct sk_buff *skb; int err; struct rt6_info *rt = (struct rt6_info *)*dstp; + unsigned int hard_header_len = rt->dst.dev->hard_header_len; + unsigned int needed_headroom = rt->dst.dev->needed_headroom; + unsigned int needed_tailroom = rt->dst.dev->needed_tailroom; if (length > rt->dst.dev->mtu) { ipv6_local_error(sk, EMSGSIZE, fl6, rt->dst.dev->mtu);
@@ -619,11 +622,13 @@ static int rawv6_send_hdrinc(struct sock *sk, void *from, int length, goto out; skb = sock_alloc_send_skb(sk, - length + LL_ALLOCATED_SPACE(rt->dst.dev) + 15, + length + LL_ALIGN(hard_header_len + + needed_headroom + + needed_tailroom) + 15, flags & MSG_DONTWAIT, &err); if (skb == NULL) goto error; - skb_reserve(skb, LL_RESERVED_SPACE(rt->dst.dev)); + skb_reserve(skb, LL_ALIGN(hard_header_len + needed_headroom)); skb->priority = sk->sk_priority; skb->mark = sk->sk_mark;