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LibC: Don't change the stack canary across function boundaries

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Tim Schumacher 2022-06-07 15:59:05 +02:00 • committed by Linus Groh
parent 75e8b1305d
commit a880457380
1 changed files with 8 additions and 3 deletions
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11
Userland/Libraries/LibC/crt0.cpp
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@ -33,10 +33,15 @@ NAKED void _start(int, char**, char**)
int _entry(int argc, char** argv, char** env) int _entry(int argc, char** argv, char** env)
{ {
size_t original_stack_chk = __stack_chk_guard; size_t original_stack_chk = __stack_chk_guard;
arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
if (__stack_chk_guard == 0) // We can't directly overwrite __stack_chk_guard using arc4random_buf,
__stack_chk_guard = original_stack_chk; // as it doesn't know that the stack canary changed and it would instantly
// cause a stack protector failure when returning.
size_t new_stack_chk = 0;
arc4random_buf(&new_stack_chk, sizeof(new_stack_chk));
if (new_stack_chk != 0)
__stack_chk_guard = new_stack_chk;
environ = env; environ = env;
__environ_is_malloced = false; __environ_is_malloced = false;