From: Jiri Pirko <jpirko@redhat.com> Date: Thu, 23 Oct 2008 15:35:58 +0200 Subject: [net] ipv4: fix byte value boundary check Message-id: 20081023153558.1df9e92f@psychotron.englab.brq.redhat.com O-Subject: [RHEL5.4 patch] BZ468148 ipv4: Fix byte value boundary check in do_ip_getsockopt() Bugzilla: 468148 RH-Acked-by: Neil Horman <nhorman@redhat.com> RH-Acked-by: David Miller <davem@redhat.com> RH-Acked-by: Anton Arapov <aarapov@redhat.com> BZ468148 https://bugzilla.redhat.com/show_bug.cgi?id=468148 Description: If we try to grab a char sized socket option value, as in: unsigned char ttl = 255; socklen_t len = sizeof(ttl); setsockopt(socket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, &len); getsockopt(socket, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, &len); The ttl returned will be wrong on big-endian, and on both little- endian and big-endian the next three bytes in userspace are written with garbage. It's because of this test in do_ip_getsockopt(): if (len < sizeof(int) && len > 0 && val>=0 && val<255) { It should allow a 'val' of 255 to pass here, but it doesn't so it copies a full 'int' back to userspace. On little-endian that will write the correct value into the location but it spams on the next three bytes in userspace. On big endian it writes the wrong value into the location and spams the next three bytes. Upstream: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=951e07c930f5f66b676eaa4c32a1b0d8e2d7d06a Brew: https://brewweb.devel.redhat.com/taskinfo?taskID=1536585 Test: Booted and tested with reproducer on x86_64, ppc64. Works fine. Jirka diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index a107827..e9180d9 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1144,7 +1144,7 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname, } release_sock(sk); - if (len < sizeof(int) && len > 0 && val>=0 && val<255) { + if (len < sizeof(int) && len > 0 && val>=0 && val<=255) { unsigned char ucval = (unsigned char)val; len = 1; if(put_user(len, optlen))