The second memcpy in lowpan_iphc_mcast_ctx_addr_compress() uses
&data[1] as destination and &ipaddr->s6_addr[11] as source, but
both should be offset by one: &data[2] and &ipaddr->s6_addr[12]
respectively.
This off-by-one has two consequences:
1. data[1] is overwritten with s6_addr[11], corrupting the RIID
field in the compressed multicast address
2. data[5] is never written, so uninitialized kernel stack memory
is transmitted over the network via lowpan_push_hc_data(),
leaking kernel stack contents
The correct inline data layout must match what the decompression
function lowpan_uncompress_multicast_ctx_daddr() expects:
data[0..1] = s6_addr[1..2] (flags/scope + RIID)
data[2..5] = s6_addr[12..15] (group ID)
Also zero-initialize the data array as a defensive measure against
similar bugs in the future.
Fixes: 5609c185f24d ("6lowpan: iphc: add support for stateful compression")
Reported-by: Yizhou Zhao <[email protected]>
Reported-by: Yuxiang Yang <[email protected]>
Reported-by: Ao Wang <[email protected]>
Reported-by: Xuewei Feng <[email protected]>
Reported-by: Qi Li <[email protected]>
Reported-by: Ke Xu <[email protected]>
Assisted-by: GLM:GLM-5.1
Signed-off-by: Yizhou Zhao <[email protected]>
---
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index e116d30..37eaff3 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -1086,12 +1086,12 @@ static u8 lowpan_iphc_mcast_ctx_addr_compress(u8
**hc_ptr,
const struct lowpan_iphc_ctx *ctx,
const struct in6_addr *ipaddr)
{
- u8 data[6];
+ u8 data[6] = {};
/* flags/scope, reserved (RIID) */
memcpy(data, &ipaddr->s6_addr[1], 2);
/* group ID */
- memcpy(&data[1], &ipaddr->s6_addr[11], 4);
+ memcpy(&data[2], &ipaddr->s6_addr[12], 4);
lowpan_push_hc_data(hc_ptr, data, 6);
return LOWPAN_IPHC_DAM_00;
--
2.43.0
