Messages in this thread Patch in this message | | | Subject | Re: PROBLEM: System call 'sendmsg' of process ospfd (quagga) causes kernel oops | From | Eric Dumazet <> | Date | Tue, 18 Oct 2011 14:56:00 +0200 |
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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: > > > > 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 <evonlanthen@gmail.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Timo Teräs <timo.teras@iki.fi> 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;
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