Re: [PATCH net] netfilter: nf_tables: fix pointer math issue in nft_byteorder_eval()

[Pablo Neira Ayuso]

On Fri, Nov 03, 2023 at 10:18:01AM +0100, Florian Westphal wrote:
> Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> > The problem is in nft_byteorder_eval() where we are iterating through a
> > loop and writing to dst[0], dst[1], dst[2] and so on...  On each
> > iteration we are writing 8 bytes.  But dst[] is an array of u32 so each
> > element only has space for 4 bytes.  That means that every iteration
> > overwrites part of the previous element.
> > 
> > I spotted this bug while reviewing commit caf3ef7468f7 ("netfilter:
> > nf_tables: prevent OOB access in nft_byteorder_eval") which is a related
> > issue.  I think that the reason we have not detected this bug in testing
> > is that most of time we only write one element.
> 
> LGTM, thanks Dan.  We will route this via nf.git.

Thanks for your patch.

One question, is this update really required?

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 3bbd13ab1ecf..b157c5cafd14 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -178,9 +178,9 @@ static inline __be32 nft_reg_load_be32(const u32 *sreg)
        return *(__force __be32 *)sreg;
 }

-static inline void nft_reg_store64(u32 *dreg, u64 val)
+static inline void nft_reg_store64(u64 *dreg, u64 val)
 {
-       put_unaligned(val, (u64 *)dreg);
+       put_unaligned(val, dreg);
 }

 static inline u64 nft_reg_load64(const u32 *sreg)

because one of the goals of nft_reg_store64() is to avoid that caller
casts the register to 64-bits.