[PATCH 5.15.y] net/ipv6: ioam6: prevent schema length wraparound in trace fill

[Li hongliang <1468888505@139.com>]

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: Li hongliang <1468888505@139.com>
---
 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 bb7ad0d1cacf..765b87c18a4c 100644
--- a/net/ipv6/ioam6.c
+++ b/net/ipv6/ioam6.c
@@ -645,7 +645,7 @@ 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)
+				    unsigned int sclen)
 {
 	struct __kernel_sock_timeval ts;
 	u64 raw64;
@@ -863,7 +863,7 @@ void ioam6_fill_trace_data(struct sk_buff *skb,
 			   struct ioam6_trace_hdr *trace)
 {
 	struct ioam6_schema *sc;
-	u8 sclen = 0;
+	unsigned int sclen = 0;
 
 	/* Skip if Overflow flag is set
 	 */
-- 
2.34.1