[PATCH v3 1/2] tools/libs/stat: use memcpy instead of strncpy in getBridge

* [PATCH v3 1/2] tools/libs/stat: use memcpy instead of strncpy in getBridge
@ 2020-10-07 13:57 Bertrand Marquis
  2020-10-07 13:57 ` [PATCH v3 2/2] tool/libs/light: Fix libxenlight gcc warning Bertrand Marquis
  2020-10-14 10:58 ` [PATCH v3 1/2] tools/libs/stat: use memcpy instead of strncpy in getBridge Bertrand Marquis
  0 siblings, 2 replies; 6+ messages in thread
From: Bertrand Marquis @ 2020-10-07 13:57 UTC (permalink / raw)
  To: xen-devel; +Cc: jgross, Ian Jackson, Wei Liu

Use memcpy in getBridge to prevent gcc warnings about truncated
strings. We know that we might truncate it, so the gcc warning
here is wrong.
Revert previous change changing buffer sizes as bigger buffers
are not needed.

Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
---
Changes in v3:
 Do a memset 0 on destination buffer and use MIN between string length
 and resultLen - 1.
Changes in v2:
 Use MIN between string length of de->d_name and resultLen to copy only
 the minimum size required and prevent crossing to from an unallocated
 space.
---
 tools/libs/stat/xenstat_linux.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tools/libs/stat/xenstat_linux.c b/tools/libs/stat/xenstat_linux.c
index d2ee6fda64..e0d242e1bc 100644
--- a/tools/libs/stat/xenstat_linux.c
+++ b/tools/libs/stat/xenstat_linux.c
@@ -29,6 +29,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <regex.h>
+#include <xen-tools/libs.h>
 
 #include "xenstat_priv.h"
 
@@ -78,8 +79,14 @@ static void getBridge(char *excludeName, char *result, size_t resultLen)
 				sprintf(tmp, "/sys/class/net/%s/bridge", de->d_name);
 
 				if (access(tmp, F_OK) == 0) {
-					strncpy(result, de->d_name, resultLen);
-					result[resultLen - 1] = 0;
+					/*
+					 * Do not use strncpy to prevent compiler warning with
+					 * gcc >= 10.0
+					 * If de->d_name is longer then resultLen we truncate it
+					 */
+					memset(result, 0, resultLen);
+					memcpy(result, de->d_name, MIN(strnlen(de->d_name,
+									NAME_MAX),resultLen - 1));
 				}
 		}
 	}
@@ -264,7 +271,7 @@ int xenstat_collect_networks(xenstat_node * node)
 {
 	/* Helper variables for parseNetDevLine() function defined above */
 	int i;
-	char line[512] = { 0 }, iface[16] = { 0 }, devBridge[256] = { 0 }, devNoBridge[257] = { 0 };
+	char line[512] = { 0 }, iface[16] = { 0 }, devBridge[16] = { 0 }, devNoBridge[17] = { 0 };
 	unsigned long long rxBytes, rxPackets, rxErrs, rxDrops, txBytes, txPackets, txErrs, txDrops;
 
 	struct priv_data *priv = get_priv_data(node->handle);
-- 
2.17.1



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