[PATCH] tls: Check return value of get_cipher_desc in fill_sg_out

[Wentao Liang]

The function get_cipher_desc() may return NULL if the cipher type is
invalid or unsupported. In fill_sg_out(), the return value is used
without any checks, which could lead to a NULL pointer dereference.

This patch adds a DEBUG_NET_WARN_ON_ONCE check to ensure that
cipher_desc is valid and offloadable before proceeding. This prevents
potential crashes and provides a clear warning in debug builds.

Fixes: 8db44ab26beb ("tls: rename tls_cipher_size_desc to tls_cipher_desc")
Cc: stable@xxxxxxxxxxxxxxx # 6.6+
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
---
 net/tls/tls_device_fallback.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/tls/tls_device_fallback.c b/net/tls/tls_device_fallback.c
index f9e3d3d90dcf..0f93a0833ec2 100644
--- a/net/tls/tls_device_fallback.c
+++ b/net/tls/tls_device_fallback.c
@@ -306,6 +306,7 @@ static void fill_sg_out(struct scatterlist sg_out[3], void *buf,
 {
 	const struct tls_cipher_desc *cipher_desc =
 		get_cipher_desc(tls_ctx->crypto_send.info.cipher_type);
+	DEBUG_NET_WARN_ON_ONCE(!cipher_desc || !cipher_desc->offloadable);
 
 	sg_set_buf(&sg_out[0], dummy_buf, sync_size);
 	sg_set_buf(&sg_out[1], nskb->data + tcp_payload_offset, payload_len);
-- 
2.42.0.windows.2