ef0366eb4
Denys Vlasenko
2017-07-22
Subject
libbb: avoid malloc/free in bb_unsetenv()
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libbb/xfuncs_printf.c+21 -13
| @@ -344,20 +344,28 @@ void FAST_FUNC xsetenv(const char *key, const char *value) | |
| */ | |
| void FAST_FUNC bb_unsetenv(const char *var) | |
| { | |
| - | char *tp = strchr(var, '='); |
| - | |
| - | if (!tp) { |
| - | unsetenv(var); |
| - | return; |
| + | 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); |
| + | } |
| } | |
| - | |
| - | /* 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 :( */ |
| - | tp = xstrndup(var, tp - var); |
| - | unsetenv(tp); |
| + | unsetenv(var); |
| free(tp); | |
| } | |