[PATCH nf-next] netfilter: nft_payload: only cancel tracking for clobbered dregs

[Pablo Neira Ayuso <pablo@netfilter.org>]

payload expression might use more than one single register and clobber
previous data, reset tracking for the remaining registers too.

Fixes: a7c176bf9f0e ("netfilter: nft_payload: track register operations")
Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nft_payload.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 5cc06aef4345..431f70c8bc15 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -210,6 +210,23 @@ static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
 	return -1;
 }
 
+static void nft_update_reg_track(struct nft_regs_track *track,
+				 const struct nft_expr *expr, u8 dreg, u8 len)
+{
+	unsigned int regcount;
+	int i;
+
+	track->regs[dreg].selector = expr;
+	track->regs[dreg].bitwise = NULL;
+
+	dreg++;
+	regcount = DIV_ROUND_UP(len, NFT_REG32_SIZE);
+	for (i = 1; i < regcount; i++, dreg++) {
+		track->regs[dreg].selector = NULL;
+		track->regs[dreg].bitwise = NULL;
+	}
+}
+
 static bool nft_payload_reduce(struct nft_regs_track *track,
 			       const struct nft_expr *expr)
 {
@@ -218,8 +235,7 @@ static bool nft_payload_reduce(struct nft_regs_track *track,
 
 	if (!track->regs[priv->dreg].selector ||
 	    track->regs[priv->dreg].selector->ops != expr->ops) {
-		track->regs[priv->dreg].selector = expr;
-		track->regs[priv->dreg].bitwise = NULL;
+		nft_update_reg_track(track, expr, priv->dreg, priv->len);
 		return false;
 	}
 
@@ -227,8 +243,7 @@ static bool nft_payload_reduce(struct nft_regs_track *track,
 	if (priv->base != payload->base ||
 	    priv->offset != payload->offset ||
 	    priv->len != payload->len) {
-		track->regs[priv->dreg].selector = expr;
-		track->regs[priv->dreg].bitwise = NULL;
+		nft_update_reg_track(track, expr, priv->dreg, priv->len);
 		return false;
 	}
 
-- 
2.30.2