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| author | David S. Miller <davem@davemloft.net> | 2015-10-23 02:49:41 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-10-23 02:49:41 -0700 |
| commit | ec3661b42257d9a06cf0d318175623ac7a660113 (patch) | |
| tree | 00351145ca8f839024370cf1909358845357bf3a | |
| parent | c80dbe04612986fd6104b4a1be21681b113b5ac9 (diff) | |
| parent | b72a2b01b686f242028038f630555513c9e4de38 (diff) | |
Merge branch 'ipv6-overflow-arith'
Hannes Frederic Sowa says:
====================
overflow-arith: begin to add support for overflow builtins functions
I add a new header, linux/overflow-arith.h, as the central place to add
overflow and wrap-around checking functions. The reason I am doing so
is that it can make use of compiler supported builtin functions which
can leverage hardware.
As I need this for a fix in the ipv6 stack, which is also included in
this series, I propose to add it sooner than later over Davem's net
tree. This is also the reason why I start slowly with only the one
function I need at this time.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | include/linux/compiler-gcc.h | 4 | ||||
| -rw-r--r-- | include/linux/overflow-arith.h | 18 | ||||
| -rw-r--r-- | net/ipv6/ip6_output.c | 6 |
3 files changed, 27 insertions, 1 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index dfaa7b3e9ae9..82c159e0532a 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -237,6 +237,10 @@ #define KASAN_ABI_VERSION 3 #endif +#if GCC_VERSION >= 50000 +#define CC_HAVE_BUILTIN_OVERFLOW +#endif + #endif /* gcc version >= 40000 specific checks */ #if !defined(__noclone) diff --git a/include/linux/overflow-arith.h b/include/linux/overflow-arith.h new file mode 100644 index 000000000000..e12ccf854a70 --- /dev/null +++ b/include/linux/overflow-arith.h @@ -0,0 +1,18 @@ +#pragma once + +#include <linux/kernel.h> + +#ifdef CC_HAVE_BUILTIN_OVERFLOW + +#define overflow_usub __builtin_usub_overflow + +#else + +static inline bool overflow_usub(unsigned int a, unsigned int b, + unsigned int *res) +{ + *res = a - b; + return *res > a ? true : false; +} + +#endif diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index d03d6da772f3..8dddb45c433e 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -28,6 +28,7 @@ #include <linux/errno.h> #include <linux/kernel.h> +#include <linux/overflow-arith.h> #include <linux/string.h> #include <linux/socket.h> #include <linux/net.h> @@ -584,7 +585,10 @@ int ip6_fragment(struct sock *sk, struct sk_buff *skb, if (np->frag_size) mtu = np->frag_size; } - mtu -= hlen + sizeof(struct frag_hdr); + + if (overflow_usub(mtu, hlen + sizeof(struct frag_hdr), &mtu) || + mtu <= 7) + goto fail_toobig; frag_id = ipv6_select_ident(net, &ipv6_hdr(skb)->daddr, &ipv6_hdr(skb)->saddr); |