netfilter: nf_tables: fix pointer math issue in nft_byteorder_eval()

JIRA: https://issues.redhat.com/browse/RHEL-21443
Upstream Status: commit c301f09

Conflicts:
 	include/net/netfilter/nf_tables.h
 	net/netfilter/nft_byteorder.c

Context, we lack
7278b3c ("netfilter: nf_tables: add and use BE register load-store helpers"),
which is a sparse-cleanup, not a functional fix.

commit c301f09
Author: Dan Carpenter <dan.carpenter@linaro.org>
Date:   Fri Nov 3 09:42:51 2023 +0300

    netfilter: nf_tables: fix pointer math issue in nft_byteorder_eval()

    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 caf3ef7 ("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: ce1e798 ("netfilter: nft_byteorder: provide 64bit le/be conversion")
    Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Signed-off-by: Florian Westphal <fwestpha@redhat.com>

Author: fw-strlen

include/net/netfilter/nf_tables.h

@@ -150,9 +150,9 @@ static inline u16 nft_reg_load16(const u32 *sreg)
 	return *(u16 *)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)

net/netfilter/nft_byteorder.c

@@ -38,20 +38,22 @@ 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], be64_to_cpu(src64));
+				nft_reg_store64(&dst64[i],
+						be64_to_cpu((__force __be64)src64));
 			}
 			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(&dst[i], src64);
+				nft_reg_store64(&dst64[i], src64);
 			}
 			break;
 		}

net/netfilter/nft_meta.c

@@ -63,7 +63,7 @@ nft_meta_get_eval_time(enum nft_meta_keys key,
 {
 	switch (key) {
 	case NFT_META_TIME_NS:
-		nft_reg_store64(dest, ktime_get_real_ns());
+		nft_reg_store64((u64 *)dest, ktime_get_real_ns());
 		break;
 	case NFT_META_TIME_DAY:
 		nft_reg_store8(dest, nft_meta_weekday());