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authorWillem de Bruijn <willemb@google.com>2021-03-01 15:09:44 +0000
committerDavid S. Miller <davem@davemloft.net>2021-03-01 15:25:24 -0800
commitb228c9b058760500fda5edb3134527f629fc2dc3 (patch)
treeda9c298ac2224e735f2d0f56c28a48e7324c8701 /net
parent2353db75c3db1dd26ff9c8feccfd3543a9cb73be (diff)
net: expand textsearch ts_state to fit skb_seq_state
The referenced commit expands the skb_seq_state used by skb_find_text with a 4B frag_off field, growing it to 48B. This exceeds container ts_state->cb, causing a stack corruption: [ 73.238353] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: skb_find_text+0xc5/0xd0 [ 73.247384] CPU: 1 PID: 376 Comm: nping Not tainted 5.11.0+ #4 [ 73.252613] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 73.260078] Call Trace: [ 73.264677] dump_stack+0x57/0x6a [ 73.267866] panic+0xf6/0x2b7 [ 73.270578] ? skb_find_text+0xc5/0xd0 [ 73.273964] __stack_chk_fail+0x10/0x10 [ 73.277491] skb_find_text+0xc5/0xd0 [ 73.280727] string_mt+0x1f/0x30 [ 73.283639] ipt_do_table+0x214/0x410 The struct is passed between skb_find_text and its callbacks skb_prepare_seq_read, skb_seq_read and skb_abort_seq read through the textsearch interface using TS_SKB_CB. I assumed that this mapped to skb->cb like other .._SKB_CB wrappers. skb->cb is 48B. But it maps to ts_state->cb, which is only 40B. skb->cb was increased from 40B to 48B after ts_state was introduced, in commit 3e3850e989c5 ("[NETFILTER]: Fix xfrm lookup in ip_route_me_harder/ip6_route_me_harder"). Increase ts_state.cb[] to 48 to fit the struct. Also add a BUILD_BUG_ON to avoid a repeat. The alternative is to directly add a dependency from textsearch onto linux/skbuff.h, but I think the intent is textsearch to have no such dependencies on its callers. Link: https://bugzilla.kernel.org/show_bug.cgi?id=211911 Fixes: 97550f6fa592 ("net: compound page support in skb_seq_read") Reported-by: Kris Karas <bugs-a17@moonlit-rail.com> Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/skbuff.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 545a472273a5..c421c8f80925 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3659,6 +3659,8 @@ unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
struct ts_state state;
unsigned int ret;
+ BUILD_BUG_ON(sizeof(struct skb_seq_state) > sizeof(state.cb));
+
config->get_next_block = skb_ts_get_next_block;
config->finish = skb_ts_finish;