string_utils: work around an MSan false positive

MSan doesn't instrument stpncpy (https://github.com/google/sanitizers/issues/926), which causes the fuzzer to fail with: ``` $ cat ../minimized-from-740f56329efc60eab59b8194132b712a873e88a3 lxc.console.size=123 $ ./out/fuzz-lxc-config-read ../minimized-from-740f56329efc60eab59b8194132b712a873e88a3 INFO: Seed: 3561494591 INFO: Loaded 1 modules (18795 inline 8-bit counters): 18795 [0x866b98, 0x86b503), INFO: Loaded 1 PC tables (18795 PCs): 18795 [0x86b508,0x8b4bb8), ./out/fuzz-lxc-config-read: Running 1 inputs 1 time(s) each. Running: ../minimized-from-740f56329efc60eab59b8194132b712a873e88a3 ==850885==WARNING: MemorySanitizer: use-of-uninitialized-value #0 0x6b3e7f in parse_byte_size_string /home/vagrant/lxc/src/lxc/string_utils.c:912:6 #1 0x550991 in set_config_console_size /home/vagrant/lxc/src/lxc/confile.c:2483:8 #2 0x5346e2 in parse_line /home/vagrant/lxc/src/lxc/confile.c:2962:9 #3 0x64b3cd in lxc_file_for_each_line_mmap /home/vagrant/lxc/src/lxc/parse.c:125:9 #4 0x53340c in lxc_config_read /home/vagrant/lxc/src/lxc/confile.c:3039:9 #5 0x4e7ec2 in LLVMFuzzerTestOneInput /home/vagrant/lxc/src/tests/fuzz-lxc-config-read.c:23:2 #6 0x44ad2c in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/vagrant/lxc/out/fuzz-lxc-config-read+0x44ad2c) #7 0x42ca4d in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/vagrant/lxc/out/fuzz-lxc-config-read+0x42ca4d) #8 0x433af0 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/vagrant/lxc/out/fuzz-lxc-config-read+0x433af0) #9 0x423ff6 in main (/home/vagrant/lxc/out/fuzz-lxc-config-read+0x423ff6) #10 0x7f79bdc89081 in __libc_start_main (/lib64/libc.so.6+0x27081) #11 0x42402d in _start (/home/vagrant/lxc/out/fuzz-lxc-config-read+0x42402d) Uninitialized value was created by an allocation of 'dup' in the stack frame of function 'parse_byte_size_string' #0 0x6b3330 in parse_byte_size_string /home/vagrant/lxc/src/lxc/string_utils.c:901 SUMMARY: MemorySanitizer: use-of-uninitialized-value /home/vagrant/lxc/src/lxc/string_utils.c:912:6 in parse_byte_size_string Exiting ``` Closes https://oss-fuzz.com/testcase-detail/5829890470445056Signed-off-by: Evgeny Vereshchagin <evvers@ya.ru>

string_utils: work around an MSan false positive
f6727edb · Evgeny Vereshchagin · cf0f7aba · f6727edb
Commit f6727edb authored Mar 28, 2021 by Evgeny Vereshchagin
Hide whitespace changes
Inline Side-by-side

Showing with 1 addition and 1 deletion

string_utils.c src/lxc/string_utils.c +1 -1

No files found.
--- a/src/lxc/string_utils.c
+++ b/src/lxc/string_utils.c
@@ -902,7 +902,7 @@ int parse_byte_size_string(const char *s, long long int *converted)
 	int ret, suffix_len;
 	long long int conv, mltpl;
 	char *end;
-	char dup[INTTYPE_TO_STRLEN(long long int)];
+	char dup[INTTYPE_TO_STRLEN(long long int)] = {0};
 	char suffix[3] = {0};
 	if (is_empty_string(s))