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Message-ID: <20240206104336.ctigqpkunom2ufmn@lion.mk-sys.cz>
Date: Tue, 6 Feb 2024 11:43:36 +0100
From: Michal Kubecek <mkubecek@...e.cz>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Florian Westphal <fw@...len.de>,
Pablo Neira Ayuso <pablo@...filter.org>,
Jozsef Kadlecsik <kadlec@...filter.org>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
netfilter-devel@...r.kernel.org, coreteam@...filter.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel-janitors@...r.kernel.org, andrea.mattiazzo@...e.com
Subject: Re: [PATCH net] netfilter: nf_tables: fix pointer math issue in
nft_byteorder_eval()
On Fri, Nov 03, 2023 at 09:42:51AM +0300, Dan Carpenter 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.
>
> Fixes: ce1e7989d989 ("netfilter: nft_byteorder: provide 64bit le/be conversion")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> include/net/netfilter/nf_tables.h | 4 ++--
> net/netfilter/nft_byteorder.c | 5 +++--
> net/netfilter/nft_meta.c | 2 +-
> 3 files changed, 6 insertions(+), 5 deletions(-)
>
> 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)
> diff --git a/net/netfilter/nft_byteorder.c b/net/netfilter/nft_byteorder.c
> index e596d1a842f7..f6e791a68101 100644
> --- a/net/netfilter/nft_byteorder.c
> +++ b/net/netfilter/nft_byteorder.c
> @@ -38,13 +38,14 @@ void nft_byteorder_eval(const struct nft_expr *expr,
>
> switch (priv->size) {
> case 8: {
> + u64 *dst64 = (void *)dst;
> u64 src64;
>
> switch (priv->op) {
> case NFT_BYTEORDER_NTOH:
> for (i = 0; i < priv->len / 8; i++) {
> src64 = nft_reg_load64(&src[i]);
> - nft_reg_store64(&dst[i],
> + nft_reg_store64(&dst64[i],
> be64_to_cpu((__force __be64)src64));
> }
> break;
> @@ -52,7 +53,7 @@ void nft_byteorder_eval(const struct nft_expr *expr,
> for (i = 0; i < priv->len / 8; i++) {
> src64 = (__force __u64)
> cpu_to_be64(nft_reg_load64(&src[i]));
> - nft_reg_store64(&dst[i], src64);
> + nft_reg_store64(&dst64[i], src64);
> }
> break;
> }
I stumbled upon this when the issue got a CVE id (sigh) and I share
Andrea's (Cc-ed) concern that the fix is incomplete. While the fix,
commit c301f0981fdd ("netfilter: nf_tables: fix pointer math issue in
nft_byteorder_eval()") now, fixes the destination side, src is still
a pointer to u32, i.e. we are reading 64-bit values with relative
offsets which are multiples of 32 bits.
Shouldn't we fix this as well, e.g. like indicated below?
Michal
------------------------------------------------------------------------------
diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 001226c34621..bb4b83ea2908 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -183,9 +183,9 @@ static inline void nft_reg_store64(u64 *dreg, u64 val)
put_unaligned(val, dreg);
}
-static inline u64 nft_reg_load64(const u32 *sreg)
+static inline u64 nft_reg_load64(const u64 *sreg)
{
- return get_unaligned((u64 *)sreg);
+ return get_unaligned(sreg);
}
static inline void nft_data_copy(u32 *dst, const struct nft_data *src,
diff --git a/net/netfilter/nft_byteorder.c b/net/netfilter/nft_byteorder.c
index f6e791a68101..2a64c69ed507 100644
--- a/net/netfilter/nft_byteorder.c
+++ b/net/netfilter/nft_byteorder.c
@@ -39,21 +39,22 @@ void nft_byteorder_eval(const struct nft_expr *expr,
switch (priv->size) {
case 8: {
u64 *dst64 = (void *)dst;
- u64 src64;
+ u64 *src64 = (void *)src;
+ u64 val64;
switch (priv->op) {
case NFT_BYTEORDER_NTOH:
for (i = 0; i < priv->len / 8; i++) {
- src64 = nft_reg_load64(&src[i]);
+ val64 = nft_reg_load64(&src64[i]);
nft_reg_store64(&dst64[i],
- be64_to_cpu((__force __be64)src64));
+ be64_to_cpu((__force __be64)val64));
}
break;
case NFT_BYTEORDER_HTON:
for (i = 0; i < priv->len / 8; i++) {
- src64 = (__force __u64)
- cpu_to_be64(nft_reg_load64(&src[i]));
- nft_reg_store64(&dst64[i], src64);
+ val64 = (__force __u64)
+ cpu_to_be64(nft_reg_load64(&src64[i]));
+ nft_reg_store64(&dst64[i], val64);
}
break;
}
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