netfilter: nf_osf: avoid passing pointer to local var

gcc-10 points out that a code path exists where a pointer to a stack
variable may be passed back to the caller:

net/netfilter/nfnetlink_osf.c: In function 'nf_osf_hdr_ctx_init':
cc1: warning: function may return address of local variable [-Wreturn-local-addr]
net/netfilter/nfnetlink_osf.c:171:16: note: declared here
  171 |  struct tcphdr _tcph;
      |                ^~~~~

I am not sure whether this can happen in practice, but moving the
variable declaration into the callers avoids the problem.

Fixes: 31a9c29210e2 ("netfilter: nf_osf: add struct nf_osf_hdr_ctx")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index 9f5dea0..916a3c7 100644 (file)
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -165,12 +165,12 @@ static bool nf_osf_match_one(const struct sk_buff *skb,
 static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
                                                const struct sk_buff *skb,
                                                const struct iphdr *ip,
-                                               unsigned char *opts)
+                                               unsigned char *opts,
+                                               struct tcphdr *_tcph)
 {
        const struct tcphdr *tcp;
-       struct tcphdr _tcph;
 
-       tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
+       tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), _tcph);
        if (!tcp)
                return NULL;
 
@@ -205,10 +205,11 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family,
        int fmatch = FMATCH_WRONG;
        struct nf_osf_hdr_ctx ctx;
        const struct tcphdr *tcp;
+       struct tcphdr _tcph;
 
        memset(&ctx, 0, sizeof(ctx));
 
-       tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
+       tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
        if (!tcp)
                return false;
 
@@ -265,10 +266,11 @@ bool nf_osf_find(const struct sk_buff *skb,
        const struct nf_osf_finger *kf;
        struct nf_osf_hdr_ctx ctx;
        const struct tcphdr *tcp;
+       struct tcphdr _tcph;
 
        memset(&ctx, 0, sizeof(ctx));
 
-       tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
+       tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
        if (!tcp)
                return false;