[PATCH 01/28] [v2] netfilter: nf_tables: avoid uninitialized variable warning

Arnd Bergmann
2016-10-17T22:06:24Z

The newly added nft_range_eval() function handles the two possible
nft range operations, but as the compiler warning points out,
any unexpected value would lead to the 'mismatch' variable being
used without being initialized:

net/netfilter/nft_range.c: In function 'nft_range_eval':
net/netfilter/nft_range.c:45:5: error: 'mismatch' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This removes the variable in question and instead moves the
condition into the switch itself, which is potentially more
efficient than adding a bogus 'default' clause as in my
first approach, and is nicer than using the 'uninitialized_var'
macro.

Fixes: 0f3cd9b36977 ("netfilter: nf_tables: add range expression")
Link: http://patchwork.ozlabs.org/patch/677114/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
net/netfilter/nft_range.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

Cc: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nft_range.c b/net/netfilter/nft_range.c
index c6d5358..2dd80f4 100644
--- a/net/netfilter/nft_range.c
+++ b/net/netfilter/nft_range.c
@@ -28,22 +28,20 @@ static void nft_range_eval(const struct nft_expr *expr,
const struct nft_pktinfo *pkt)
{
const struct nft_range_expr *priv = nft_expr_priv(expr);
- bool mismatch;
int d1, d2;

d1 = memcmp(&regs->data[priv->sreg], &priv->data_from, priv->len);
d2 = memcmp(&regs->data[priv->sreg], &priv->data_to, priv->len);
switch (priv->op) {
case NFT_RANGE_EQ:
- mismatch = (d1 < 0 || d2 > 0);
+ if (d1 < 0 || d2 > 0)
+ regs->verdict.code = NFT_BREAK;
break;
case NFT_RANGE_NEQ:
- mismatch = (d1 >= 0 && d2 <= 0);
+ if (d1 >= 0 && d2 <= 0)
+ regs->verdict.code = NFT_BREAK;
break;
}
-
- if (mismatch)
- regs->verdict.code = NFT_BREAK;
}

static const struct nla_policy nft_range_policy[NFTA_RANGE_MAX + 1] = {
--
2.9.0