[PATCH] net: gro: fix a potential crash in skb_gro_reset_offset
From: Eric Dumazet <hidden>
Date: 2012-10-07 08:28:11
From: Eric Dumazet <redacted> Before accessing skb first fragment, better make sure there is one. This is probably not needed for old kernels, since an ethernet frame cannot contain only an ethernet header, but the recent GRO addition to tunnels makes this patch needed. Also skb_gro_reset_offset() can be static, it actually allows compiler to inline it. Signed-off-by: Eric Dumazet <redacted> Cc: Herbert Xu <herbert@gondor.apana.org.au> --- include/linux/netdevice.h | 1 - net/core/dev.c | 14 ++++++++------ 2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 01646aa..a659fd0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -1663,7 +1663,6 @@ extern int netpoll_trap(void); #endif extern int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb); -extern void skb_gro_reset_offset(struct sk_buff *skb); static inline unsigned int skb_gro_offset(const struct sk_buff *skb) {
diff --git a/net/core/dev.c b/net/core/dev.c
index 1e0a184..de2bad7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -3631,20 +3631,22 @@ gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb) } EXPORT_SYMBOL(napi_skb_finish); -void skb_gro_reset_offset(struct sk_buff *skb) +static void skb_gro_reset_offset(struct sk_buff *skb) { + const struct skb_shared_info *pinfo = skb_shinfo(skb); + const skb_frag_t *frag0 = &pinfo->frags[0]; + NAPI_GRO_CB(skb)->data_offset = 0; NAPI_GRO_CB(skb)->frag0 = NULL; NAPI_GRO_CB(skb)->frag0_len = 0; if (skb->mac_header == skb->tail && - !PageHighMem(skb_frag_page(&skb_shinfo(skb)->frags[0]))) { - NAPI_GRO_CB(skb)->frag0 = - skb_frag_address(&skb_shinfo(skb)->frags[0]); - NAPI_GRO_CB(skb)->frag0_len = skb_frag_size(&skb_shinfo(skb)->frags[0]); + pinfo->nr_frags && + !PageHighMem(skb_frag_page(frag0))) { + NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0); + NAPI_GRO_CB(skb)->frag0_len = skb_frag_size(frag0); } } -EXPORT_SYMBOL(skb_gro_reset_offset); gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb) {