From: Fernando Fernandez Mancera Non-standard targets may contain only struct xt_entry_target. mark_source_chains() nevertheless reads the target as an xt_standard_target before checking its name, potentially reading four bytes beyond a header-only target. Check that the target is standard before reading its verdict. Non-standard targets remain handled as fallthrough rules. See the following KASAN trace: BUG: KASAN: slab-out-of-bounds in translate_table+0x1660/0x1a40 [ip6_tables] Read of size 4 at addr ffff88800ed56ff8 by task rep/432 Call Trace: kasan_report+0xfa/0x120 translate_table+0x1660/0x1a40 [ip6_tables] do_ip6t_set_ctl+0x667/0xa76 [ip6_tables] nf_setsockopt+0x77/0xd0 do_sock_setsockopt+0x118/0x490 __sys_setsockopt+0xe4/0x160 __x64_sys_setsockopt+0xbd/0x190 do_syscall_64+0xde/0x4f0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 432: kasan_save_stack+0x2f/0x50 __kasan_kmalloc+0x7f/0x90 __kvmalloc_node_noprof+0x1b1/0x5c0 xt_alloc_table_info+0x3c/0xa0 do_ip6t_set_ctl+0x5ee/0xa76 [ip6_tables] nf_setsockopt+0x77/0xd0 do_sock_setsockopt+0x118/0x490 __sys_setsockopt+0xe4/0x160 __x64_sys_setsockopt+0xbd/0x190 do_syscall_64+0xde/0x4f0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: VEGA Signed-off-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/arp_tables.c | 5 +++-- net/ipv4/netfilter/ip_tables.c | 5 +++-- net/ipv6/netfilter/ip6_tables.c | 5 +++-- 3 files changed, 9 insertions(+), 6 deletions(-) diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index cf747e1e17a3..7ff3d1f0ffd4 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -371,11 +371,12 @@ static int mark_source_chains(const struct xt_table_info *newinfo, e->counters.pcnt = pos; pos += size; } else { - int newpos = t->verdict; + int newpos; if (strcmp(t->target.u.user.name, XT_STANDARD_TARGET) == 0 && - newpos >= 0) { + t->verdict >= 0) { + newpos = t->verdict; /* This a jump; chase it. */ if (!xt_find_jump_offset(offsets, newpos, newinfo->number)) diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 809441cedced..b302bd77180a 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -422,11 +422,12 @@ mark_source_chains(const struct xt_table_info *newinfo, e->counters.pcnt = pos; pos += size; } else { - int newpos = t->verdict; + int newpos; if (strcmp(t->target.u.user.name, XT_STANDARD_TARGET) == 0 && - newpos >= 0) { + t->verdict >= 0) { + newpos = t->verdict; /* This a jump; chase it. */ if (!xt_find_jump_offset(offsets, newpos, newinfo->number)) diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index 313c4aac377a..010baaa60665 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -440,11 +440,12 @@ mark_source_chains(const struct xt_table_info *newinfo, e->counters.pcnt = pos; pos += size; } else { - int newpos = t->verdict; + int newpos; if (strcmp(t->target.u.user.name, XT_STANDARD_TARGET) == 0 && - newpos >= 0) { + t->verdict >= 0) { + newpos = t->verdict; /* This a jump; chase it. */ if (!xt_find_jump_offset(offsets, newpos, newinfo->number)) -- 2.47.3