3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet <edumazet@xxxxxxxxxx> [ Upstream commit 16fad69cfe4adbbfa813de516757b87bcae36d93 ] Chrome OS team reported a crash on a Pixel ChromeBook in TCP stack : https://code.google.com/p/chromium/issues/detail?id=182056 commit a21d45726acac (tcp: avoid order-1 allocations on wifi and tx path) did a poor choice adding an 'avail_size' field to skb, while what we really needed was a 'reserved_tailroom' one. It would have avoided commit 22b4a4f22da (tcp: fix retransmit of partially acked frames) and this commit. Crash occurs because skb_split() is not aware of the 'avail_size' management (and should not be aware) Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reported-by: Mukesh Agrawal <quiche@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/linux/skbuff.h | 7 +++++-- net/ipv4/tcp.c | 2 +- net/ipv4/tcp_output.c | 1 - 3 files changed, 6 insertions(+), 4 deletions(-) --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -491,7 +491,7 @@ struct sk_buff { union { __u32 mark; __u32 dropcount; - __u32 avail_size; + __u32 reserved_tailroom; }; sk_buff_data_t inner_transport_header; @@ -1428,7 +1428,10 @@ static inline int skb_tailroom(const str */ static inline int skb_availroom(const struct sk_buff *skb) { - return skb_is_nonlinear(skb) ? 0 : skb->avail_size - skb->len; + if (skb_is_nonlinear(skb)) + return 0; + + return skb->end - skb->tail - skb->reserved_tailroom; } /** --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -773,7 +773,7 @@ struct sk_buff *sk_stream_alloc_skb(stru * Make sure that we have exactly size bytes * available to the caller, no more, no less. */ - skb->avail_size = size; + skb->reserved_tailroom = skb->end - skb->tail - size; return skb; } __kfree_skb(skb); --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1298,7 +1298,6 @@ static void __pskb_trim_head(struct sk_b eat = min_t(int, len, skb_headlen(skb)); if (eat) { __skb_pull(skb, eat); - skb->avail_size -= eat; len -= eat; if (!len) return; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html