In the version 1.32.1,in file: busybox-1.32.1/libbb/xfuncs_printf.c fuction: void FAST_FUNC bb_unsetenv(const char *var): the origin code is bellow: void FAST_FUNC bb_unsetenv(const char *var) { char onstack[128 - 16]; /* smaller stack setup code on x86 */ char *tp; tp = strchr(var, '='); if (tp) { /* In case var was putenv'ed, we can't replace '=' * with NUL and unsetenv(var) - it won't work, * env is modified by the replacement, unsetenv * sees "VAR" instead of "VAR=VAL" and does not remove it! * Horror :( */ unsigned sz = tp - var; if (sz < sizeof(onstack)) { ((char*)mempcpy(onstack, var, sz))[0] = '\0'; tp = NULL; var = onstack; } else { /* unlikely: very long var name */ var = tp = xstrndup(var, sz); } } unsetenv(var); free(tp); // --- tp maybe a NULL when sz < sizeof(onstack) } so, my idea is : if (tp != NULL) free(tp); Thanks.
busybox-1.32.1/libbb/xfuncs_printf.c: void FAST_FUNC bb_unsetenv(const char *var) { char onstack[128 - 16]; /* smaller stack setup code on x86 */ char *tp; tp = strchr(var, '='); if (tp) { /* In case var was putenv'ed, we can't replace '=' * with NUL and unsetenv(var) - it won't work, * env is modified by the replacement, unsetenv * sees "VAR" instead of "VAR=VAL" and does not remove it! * Horror :( */ unsigned sz = tp - var; if (sz < sizeof(onstack)) { ((char*)mempcpy(onstack, var, sz))[0] = '\0'; //donot use mempcpy,this maybe abort the process //I chage to snprintf(onstack, sz + 1, "%s", var); fix it tp = NULL; var = onstack; } else { /* unlikely: very long var name */ var = tp = xstrndup(var, sz); } } unsetenv(var); free(tp); // --- tp maybe a NULL when sz < sizeof(onstack) }
ISO-IEC 9899, 7.20.3.2 free() 2 ... If ptr is a null pointer, no action occurs. It is perfectly fine to free(NULL).