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* [PATCH -next] GRE: Use strlcat() for size checking
@ 2013-03-27 18:48 Geert Uytterhoeven
  2013-03-27 20:06 ` Ben Hutchings
  0 siblings, 1 reply; 3+ messages in thread
From: Geert Uytterhoeven @ 2013-03-27 18:48 UTC (permalink / raw)
  To: Pravin B Shelar, David S. Miller
  Cc: netdev, linux-kernel, linux-next, Geert Uytterhoeven

On m68k, gcc tries to be smart and turns

    strncat(name, "%d", 2);

into a call to strlen() and a 16-bit store, causing a link failure,
as arch/m68k/include/asm/string.h provides strlen() using a macro:

    ERROR: "strlen" [net/ipv4/ip_tunnel.ko] undefined!

Use strlcat() instead to avoid this, which also allows to simplify the
check for buffer overflows.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
--
Compile-tested only

http://kisskb.ellerman.id.au/kisskb/buildresult/8462108/
---
 net/ipv4/ip_tunnel.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 9d96b68..8dbe672 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -284,12 +284,11 @@ static struct net_device *__ip_tunnel_create(struct net *net,
 	if (parms->name[0])
 		strlcpy(name, parms->name, IFNAMSIZ);
 	else {
-		if (strlen(ops->kind) + 3 >= IFNAMSIZ) {
+		strlcpy(name, ops->kind, IFNAMSIZ);
+		if (strlcat(name, "%d", IFNAMSIZ) >= IFNAMSIZ) {
 			err = -E2BIG;
 			goto failed;
 		}
-		strlcpy(name, ops->kind, IFNAMSIZ);
-		strncat(name, "%d", 2);
 	}
 
 	ASSERT_RTNL();
-- 
1.7.0.4

^ permalink raw reply related	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2013-03-27 20:10 UTC | newest]

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2013-03-27 18:48 [PATCH -next] GRE: Use strlcat() for size checking Geert Uytterhoeven
2013-03-27 20:06 ` Ben Hutchings
2013-03-27 20:10   ` David Miller

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