[PATCH 6.12 048/242] net/ipv6: ioam6: prevent schema length wraparound in trace fill

Greg Kroah-Hartman
2026-04-08T18:41:18Z

From: Pengpeng Hou <pengpeng@iscas.ac.cn>

[ Upstream commit 5e67ba9bb531e1ec6599a82a065dea9040b9ce50 ]

ioam6_fill_trace_data() stores the schema contribution to the trace
length in a u8. With bit 22 enabled and the largest schema payload,
sclen becomes 1 + 1020 / 4, wraps from 256 to 0, and bypasses the
remaining-space check. __ioam6_fill_trace_data() then positions the
write cursor without reserving the schema area but still copies the
4-byte schema header and the full schema payload, overrunning the trace
buffer.

Keep sclen in an unsigned int so the remaining-space check and the write
cursor calculation both see the full schema length.

Fixes: 8c6f6fa67726 ("ipv6: ioam: IOAM Generic Netlink API")
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Reviewed-by: Justin Iurman <justin.iurman@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/ioam6.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
index b6ed67d7027c1..868a25c57b924 100644
--- a/net/ipv6/ioam6.c
+++ b/net/ipv6/ioam6.c
@@ -712,7 +712,7 @@ static void __ioam6_fill_trace_data(struct sk_buff *skb,
struct ioam6_namespace *ns,
struct ioam6_trace_hdr *trace,
struct ioam6_schema *sc,
- u8 sclen, bool is_input)
+ unsigned int sclen, bool is_input)
{
struct timespec64 ts;
ktime_t tstamp;
@@ -942,7 +942,7 @@ void ioam6_fill_trace_data(struct sk_buff *skb,
bool is_input)
{
struct ioam6_schema *sc;
- u8 sclen = 0;
+ unsigned int sclen = 0;

/* Skip if Overflow flag is set
*/
--
2.53.0