clang-tidy, starting from LLVM version 16, up to at least LLVM version
19, now checks that we detect and handle errors for snprintf() as
requested by CERT C rule ERR33-C. These warnings were logged with LLVM
version 19.1.2 (at least Debian and Fedora match):
/home/sbrivio/passt/arch.c:43:3: error: the value returned by this function should not be
disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
43 | snprintf(new_path, PATH_MAX + sizeof(".avx2"),
"%s.avx2", exe);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/arch.c:43:3: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/conf.c:577:4: error: the value returned by this function should not be
disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
577 | snprintf(netns, PATH_MAX, "/proc/%ld/ns/net",
pidval);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/conf.c:577:4: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/conf.c:579:5: error: the value returned by this function should not be
disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
579 | snprintf(userns, PATH_MAX,
"/proc/%ld/ns/user",
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
580 | pidval);
| ~~~~~~~
/home/sbrivio/passt/conf.c:579:5: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/pasta.c:105:2: error: the value returned by this function should not
be disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
105 | snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/pasta.c:105:2: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/pasta.c:242:2: error: the value returned by this function should not
be disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
242 | snprintf(uidmap, BUFSIZ, "0 %u 1", uid);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/pasta.c:242:2: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/pasta.c:243:2: error: the value returned by this function should not
be disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
243 | snprintf(gidmap, BUFSIZ, "0 %u 1", gid);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/pasta.c:243:2: note: cast the expression to void to silence this
warning
/home/sbrivio/passt/tap.c:1155:4: error: the value returned by this function should not be
disregarded; neglecting it may lead to errors [cert-err33-c,-warnings-as-errors]
1155 | snprintf(path, UNIX_PATH_MAX - 1, UNIX_SOCK_PATH, i);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sbrivio/passt/tap.c:1155:4: note: cast the expression to void to silence this
warning
Don't silence the warnings as they might actually have some merit. Add
an snprintf_check() function, instead, checking that we're not
truncating messages while printing to buffers and terminating if we
do.
Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
arch.c | 4 +++-
conf.c | 11 +++++++----
pasta.c | 7 ++++---
tap.c | 8 +++++---
util.c | 22 ++++++++++++++++++++++
util.h | 3 +++
6 files changed, 44 insertions(+), 11 deletions(-)
diff --git a/arch.c b/arch.c
index 04bebfc..edbe666 100644
--- a/arch.c
+++ b/arch.c
@@ -19,6 +19,7 @@
#include <unistd.h>
#include "log.h"
+#include "util.h"
/**
* arch_avx2_exec() - Switch to AVX2 build if supported
@@ -40,7 +41,8 @@ void arch_avx2_exec(char **argv)
if (__builtin_cpu_supports("avx2")) {
char new_path[PATH_MAX + sizeof(".avx2")];
- snprintf(new_path, PATH_MAX + sizeof(".avx2"), "%s.avx2", exe);
+ snprintf_check("Can't build AVX2 executable path", new_path,
+ PATH_MAX + sizeof(".avx2"), "%s.avx2", exe);
execve(new_path, argv, environ);
warn_perror("Can't run AVX2 build, using non-AVX2 version");
}
diff --git a/conf.c b/conf.c
index b3b5342..2122600 100644
--- a/conf.c
+++ b/conf.c
@@ -574,10 +574,13 @@ static void conf_pasta_ns(int *netns_only, char *userns, char
*netns,
if (pidval < 0 || pidval > INT_MAX)
die("Invalid PID %s", argv[optind]);
- snprintf(netns, PATH_MAX, "/proc/%ld/ns/net", pidval);
- if (!*userns)
- snprintf(userns, PATH_MAX, "/proc/%ld/ns/user",
- pidval);
+ snprintf_check("Can't build netns path", netns,
+ PATH_MAX, "/proc/%ld/ns/net", pidval);
+ if (!*userns) {
+ snprintf_check("Can't build userns path",
+ userns, PATH_MAX,
+ "/proc/%ld/ns/user", pidval);
+ }
}
}
diff --git a/pasta.c b/pasta.c
index 307fb4a..ce9ae7a 100644
--- a/pasta.c
+++ b/pasta.c
@@ -102,7 +102,8 @@ static int pasta_wait_for_ns(void *arg)
int flags = O_RDONLY | O_CLOEXEC;
char ns[PATH_MAX];
- snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
+ snprintf_check("Can't build netns path", ns,
+ PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
do {
while ((c->pasta_netns_fd = open(ns, flags)) < 0) {
if (errno != ENOENT)
@@ -239,8 +240,8 @@ void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
c->quiet = 1;
/* Configure user and group mappings */
- snprintf(uidmap, BUFSIZ, "0 %u 1", uid);
- snprintf(gidmap, BUFSIZ, "0 %u 1", gid);
+ snprintf_check("Can't build uidmap", uidmap, BUFSIZ, "0 %u 1",
uid);
+ snprintf_check("Can't build gidmap", gidmap, BUFSIZ, "0 %u 1",
gid);
if (write_file("/proc/self/uid_map", uidmap) ||
write_file("/proc/self/setgroups", "deny") ||
diff --git a/tap.c b/tap.c
index c53a39b..51eb134 100644
--- a/tap.c
+++ b/tap.c
@@ -1149,10 +1149,12 @@ int tap_sock_unix_open(char *sock_path)
char *path = addr.sun_path;
int ex, ret;
- if (*sock_path)
+ if (*sock_path) {
memcpy(path, sock_path, UNIX_PATH_MAX);
- else
- snprintf(path, UNIX_PATH_MAX - 1, UNIX_SOCK_PATH, i);
+ } else {
+ snprintf_check("Can't build UNIX domain path", path,
+ UNIX_PATH_MAX - 1, UNIX_SOCK_PATH, i);
+ }
ex = socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0);
if (ex < 0)
diff --git a/util.c b/util.c
index eba7d52..eff6787 100644
--- a/util.c
+++ b/util.c
@@ -749,3 +749,25 @@ void close_open_files(int argc, char **argv)
if (rc)
die_perror("Failed to close files leaked by parent");
}
+
+/**
+ * snprintf_check() - snprintf() wrapper, terminating on truncation
+ * @errmsg: Error string to be printed while terminating
+ * @str: Output buffer
+ * @size: Maximum size to write to @str
+ * @format: Message
+ */
+void snprintf_check(const char *errstr,
+ char *str, size_t size, const char *format, ...)
+{
+ va_list ap;
+ int rc;
+
+ va_start(ap, format);
+
+ rc = snprintf(str, size, format, ap);
+ if (rc < 0 || (size_t)rc >= size)
+ die("%s", errstr);
+
+ va_end(ap);
+}
diff --git a/util.h b/util.h
index 2c1e08e..8449d00 100644
--- a/util.h
+++ b/util.h
@@ -11,6 +11,7 @@
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
+#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <arpa/inet.h>
@@ -200,6 +201,8 @@ int write_file(const char *path, const char *buf);
int write_all_buf(int fd, const void *buf, size_t len);
int write_remainder(int fd, const struct iovec *iov, size_t iovcnt, size_t skip);
void close_open_files(int argc, char **argv);
+void snprintf_check(const char *errstr,
+ char *str, size_t size, const char *format, ...);
/**
* af_name() - Return name of an address family
--
2.43.0