netfilter: nf_tables: fix type mismatch with error return from nft_parse_u32_check

commit f1d505bb upstream.

Commit 36b701fa ("netfilter: nf_tables: validate maximum value of
u32 netlink attributes") introduced nft_parse_u32_check with a return
value of "unsigned int", yet on error it returns "-ERANGE".

This patch corrects the mismatch by changing the return value to "int",
which happens to match the actual users of nft_parse_u32_check already.

Found by Coverity, CID 1373930.

Note that commit 21a9e0f1 ("netfilter: nft_exthdr: fix error
handling in nft_exthdr_init()) attempted to address the issue, but
did not address the return type of nft_parse_u32_check.
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Cc: Laura Garcia Liebana <nevola@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 36b701fa ("netfilter: nf_tables: validate maximum value...")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

include/net/netfilter/nf_tables.h

@@ -113,7 +113,7 @@ static inline enum nft_registers nft_type_to_reg(enum nft_data_types type)
 	return type == NFT_DATA_VERDICT ? NFT_REG_VERDICT : NFT_REG_1;
 }
 
-unsigned int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest);
+int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest);
 int nft_validate_input_register(enum nft_registers reg);
 int nft_validate_output_register(enum nft_registers reg);
 int nft_validate_data_load(const struct nft_ctx *ctx, enum nft_registers reg,

net/netfilter/nf_tables_api.c

@@ -3723,7 +3723,7 @@ static int nf_tables_check_loops(const struct nft_ctx *ctx,
  *	Otherwise a 0 is returned and the attribute value is stored in the
  *	destination variable.
  */
-unsigned int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest)
+int nft_parse_u32_check(const struct nlattr *attr, int max, u32 *dest)
 {
 	u32 val;