[Xen-devel] [PATCH] tools/xenstat: Fix -Wformat-truncation= issue

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Building with GCC 8.3 on Buster identifies:

  src/xenstat_linux.c: In function 'xenstat_collect_networks':
  src/xenstat_linux.c:307:32: warning: 'snprintf' output may be truncated before
  the last format character [-Wformat-truncation=]
    snprintf(devNoBridge, 16, "p%s", devBridge);
                                  ^
  src/xenstat_linux.c:307:2: note: 'snprintf' output between 2 and 17 bytes into
  a destination of size 16
    snprintf(devNoBridge, 16, "p%s", devBridge);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

devNoBridge[] needs one charater more than devBridge[], so allocate one byte
more.  Replace a raw 16 in the snprintf() call with a sizeof() expression
instead.

Finally, libxenstat, unlike most of the rest of the Xen, doesn't use -Werror
which is why this issue went unnoticed in CI.  Fix this.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
---
 tools/xenstat/libxenstat/Makefile            | 2 +-
 tools/xenstat/libxenstat/src/xenstat_linux.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/xenstat/libxenstat/Makefile 
b/tools/xenstat/libxenstat/Makefile
index 58f9d63de5..ea115ae0e6 100644
--- a/tools/xenstat/libxenstat/Makefile
+++ b/tools/xenstat/libxenstat/Makefile
@@ -31,7 +31,7 @@ OBJECTS-$(CONFIG_NetBSD) += src/xenstat_netbsd.o
 OBJECTS-$(CONFIG_FreeBSD) += src/xenstat_freebsd.o
 SONAME_FLAGS=-Wl,$(SONAME_LDFLAG) -Wl,libxenstat.so.$(MAJOR)
 
-CFLAGS+=-fPIC
+CFLAGS+=-fPIC -Werror
 CFLAGS+=-Isrc $(CFLAGS_libxenctrl) $(CFLAGS_libxenstore) $(CFLAGS_xeninclude) 
-include $(XEN_ROOT)/tools/config.h
 
 LDLIBS-y = $(LDLIBS_libxenstore) $(LDLIBS_libxenctrl) -lyajl
diff --git a/tools/xenstat/libxenstat/src/xenstat_linux.c 
b/tools/xenstat/libxenstat/src/xenstat_linux.c
index 9421ca43c8..7530349eee 100644
--- a/tools/xenstat/libxenstat/src/xenstat_linux.c
+++ b/tools/xenstat/libxenstat/src/xenstat_linux.c
@@ -264,7 +264,7 @@ int xenstat_collect_networks(xenstat_node * node)
 {
        /* Helper variables for parseNetDevLine() function defined above */
        int i;
-       char line[512] = { 0 }, iface[16] = { 0 }, devBridge[16] = { 0 }, 
devNoBridge[16] = { 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);
@@ -304,7 +304,7 @@ int xenstat_collect_networks(xenstat_node * node)
 
        /* We get the bridge devices for use with bonding interface to get 
bonding interface stats */
        getBridge("vir", devBridge, sizeof(devBridge));
-       snprintf(devNoBridge, 16, "p%s", devBridge);
+       snprintf(devNoBridge, sizeof(devNoBridge), "p%s", devBridge);
 
        while (fgets(line, 512, priv->procnetdev)) {
                xenstat_domain *domain;
-- 
2.11.0


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel