netdev - [PATCH] net: hns: avoid uninitialized variable warning:

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 01 Jan 2016 23:27:57 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Yisen Zhuang <yisen.zhuang@...wei.com>, yankejian@...wei.com,
	lisheng011@...wei.com, huangdaode@...ilicon.com,
	salil.mehta@...wei.com, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] net: hns: avoid uninitialized variable warning:

gcc fails to see that the use of the 'last_offset' variable
in hns_nic_reuse_page() is used correctly and issues a bogus
warning:

drivers/net/ethernet/hisilicon/hns/hns_enet.c: In function 'hns_nic_reuse_page':
drivers/net/ethernet/hisilicon/hns/hns_enet.c:541:6: warning: 'last_offset' may be used uninitialized in this function [-Wmaybe-uninitialized]

This simplifies the function to make it more obvious what is
going on to both readers and compilers, which makes the warning
go away.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Compile-tested only, and complex enough that this requires a proper
review and testing before it gets apply. Please have a look at this.

diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
index 5a81dafd725e..0e30846a24f8 100644
--- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
@@ -499,50 +499,47 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int i,
 	struct hnae_desc *desc;
 	int truesize, size;
 	int last_offset;
+	bool twobufs;
+
+	twobufs = ((PAGE_SIZE < 8192) && hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048);
 
 	desc = &ring->desc[ring->next_to_clean];
 	size = le16_to_cpu(desc->rx.size);
 
-#if (PAGE_SIZE < 8192)
-	if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
+	if (twobufs) {
 		truesize = hnae_buf_size(ring);
 	} else {
 		truesize = ALIGN(size, L1_CACHE_BYTES);
 		last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
 	}
 
-#else
-	truesize = ALIGN(size, L1_CACHE_BYTES);
-	last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
-#endif
-
 	skb_add_rx_frag(skb, i, desc_cb->priv, desc_cb->page_offset + pull_len,
 			size - pull_len, truesize - pull_len);
 
 	 /* avoid re-using remote pages,flag default unreuse */
-	if (likely(page_to_nid(desc_cb->priv) == numa_node_id())) {
-#if (PAGE_SIZE < 8192)
-		if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
-			/* if we are only owner of page we can reuse it */
-			if (likely(page_count(desc_cb->priv) == 1)) {
-				/* flip page offset to other buffer */
-				desc_cb->page_offset ^= truesize;
-
-				desc_cb->reuse_flag = 1;
-				/* bump ref count on page before it is given*/
-				get_page(desc_cb->priv);
-			}
-			return;
-		}
-#endif
-		/* move offset up to the next cache line */
-		desc_cb->page_offset += truesize;
+	if (unlikely(page_to_nid(desc_cb->priv) != numa_node_id()))
+		return;
+
+	if (twobufs) {
+		/* if we are only owner of page we can reuse it */
+		if (likely(page_count(desc_cb->priv) == 1)) {
+			/* flip page offset to other buffer */
+			desc_cb->page_offset ^= truesize;
 
-		if (desc_cb->page_offset <= last_offset) {
 			desc_cb->reuse_flag = 1;
 			/* bump ref count on page before it is given*/
 			get_page(desc_cb->priv);
 		}
+		return;
+	}
+
+	/* move offset up to the next cache line */
+	desc_cb->page_offset += truesize;
+
+	if (desc_cb->page_offset <= last_offset) {
+		desc_cb->reuse_flag = 1;
+		/* bump ref count on page before it is given*/
+		get_page(desc_cb->priv);
 	}
 }
 

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html