From 98efe7c2fdd82a2822e1be8e5c5c8caed846ae76 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 24 Oct 2024 23:25:33 +0200 Subject: treewide: Comply with CERT C rule ERR33-C for snprintf() 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 terminate if the check fails. Signed-off-by: Stefano Brivio Reviewed-by: David Gibson --- util.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'util.c') diff --git a/util.c b/util.c index eba7d52..21ce0a8 100644 --- a/util.c +++ b/util.c @@ -749,3 +749,33 @@ void close_open_files(int argc, char **argv) if (rc) die_perror("Failed to close files leaked by parent"); } + +/** + * snprintf_check() - snprintf() wrapper, checking for truncation and errors + * @str: Output buffer + * @size: Maximum size to write to @str + * @format: Message + * + * Return: false on success, true on truncation or error, sets errno on failure + */ +bool snprintf_check(char *str, size_t size, const char *format, ...) +{ + va_list ap; + int rc; + + va_start(ap, format); + rc = vsnprintf(str, size, format, ap); + va_end(ap); + + if (rc < 0) { + errno = EIO; + return true; + } + + if ((size_t)rc >= size) { + errno = ENOBUFS; + return true; + } + + return false; +} -- cgit v1.2.3