[PATCH] netfilter: bitwise: fix reduce comparison

[PATCH] netfilter: bitwise: fix reduce comparison

[Jeremy Sowden]

The `nft_bitwise_reduce` function should compare the bitwise operation
in `expr` with the tracked operation associated with the destination
register of `expr`.  However, instead being called on `expr` and
`track->regs[priv->dreg].selector`, `nft_expr_priv` is called on `expr`
twice, so `nft_bitwise_reduce` returns true even when the operations
differ.

Fixes: be5650f8f47e ("netfilter: nft_bitwise: track register operations")
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
 net/netfilter/nft_bitwise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
index 7b727d3ebf9d..120a657bf8ea 100644
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -287,7 +287,7 @@ static bool nft_bitwise_reduce(struct nft_regs_track *track,
 	if (!track->regs[priv->sreg].selector)
 		return false;
 
-	bitwise = nft_expr_priv(expr);
+	bitwise = nft_expr_priv(track->regs[priv->dreg].selector);
 	if (track->regs[priv->sreg].selector == track->regs[priv->dreg].selector &&
 	    track->regs[priv->dreg].bitwise &&
 	    track->regs[priv->dreg].bitwise->ops == expr->ops &&
-- 
2.35.1

[nf PATCH v2] netfilter: bitwise: fix reduce comparisons

[Jeremy Sowden]

The `nft_bitwise_reduce` and `nft_bitwise_fast_reduce` functions should
compare the bitwise operation in `expr` with the tracked operation
associated with the destination register of `expr`.  However, instead of
being called on `expr` and `track->regs[priv->dreg].selector`,
`nft_expr_priv` is called on `expr` twice, so both reduce functions
return true even when the operations differ.

Fixes: be5650f8f47e ("netfilter: nft_bitwise: track register operations")
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
Since v1:

  * fix `nft_bitwise_fast_reduce` as well as `nft_bitwise_reduce`.
 
 net/netfilter/nft_bitwise.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
index 7b727d3ebf9d..04bd2f89afe8 100644
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -287,7 +287,7 @@ static bool nft_bitwise_reduce(struct nft_regs_track *track,
 	if (!track->regs[priv->sreg].selector)
 		return false;
 
-	bitwise = nft_expr_priv(expr);
+	bitwise = nft_expr_priv(track->regs[priv->dreg].selector);
 	if (track->regs[priv->sreg].selector == track->regs[priv->dreg].selector &&
 	    track->regs[priv->dreg].bitwise &&
 	    track->regs[priv->dreg].bitwise->ops == expr->ops &&
@@ -434,7 +434,7 @@ static bool nft_bitwise_fast_reduce(struct nft_regs_track *track,
 	if (!track->regs[priv->sreg].selector)
 		return false;
 
-	bitwise = nft_expr_priv(expr);
+	bitwise = nft_expr_priv(track->regs[priv->dreg].selector);
 	if (track->regs[priv->sreg].selector == track->regs[priv->dreg].selector &&
 	    track->regs[priv->dreg].bitwise &&
 	    track->regs[priv->dreg].bitwise->ops == expr->ops &&
-- 
2.35.1

Re: [nf PATCH v2] netfilter: bitwise: fix reduce comparisons

[Pablo Neira Ayuso]

On Sun, Mar 27, 2022 at 11:36:25PM +0100, Jeremy Sowden wrote:
> The `nft_bitwise_reduce` and `nft_bitwise_fast_reduce` functions should
> compare the bitwise operation in `expr` with the tracked operation
> associated with the destination register of `expr`.  However, instead of
> being called on `expr` and `track->regs[priv->dreg].selector`,
> `nft_expr_priv` is called on `expr` twice, so both reduce functions
> return true even when the operations differ.

Good catch, applied thanks