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Build + LibC: Enable -fstack-protector-strong in user space

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Modify the user mode runtime to insert stack canaries to find stack corruptions.

The `-fstack-protector-strong` variant was chosen because it catches more
issues than vanilla `-fstack-protector`, but doesn't have substantial
performance impact like `-fstack-protector-all`.

Details:

    -fstack-protector enables stack protection for vulnerable functions that contain:

    * A character array larger than 8 bytes.
    * An 8-bit integer array larger than 8 bytes.
    * A call to alloca() with either a variable size or a constant size bigger than 8 bytes.

    -fstack-protector-strong enables stack protection for vulnerable functions that contain:

    * An array of any size and type.
    * A call to alloca().
    * A local variable that has its address taken.

Example of it catching corrupting in the `stack-smash` test:
```
courage ~ $ ./user/Tests/LibC/stack-smash
[+] Starting the stack smash ...
Error: Stack protector failure, stack smashing detected!
Shell: Job 1 (/usr/Tests/LibC/stack-smash) Aborted
```
This commit is contained in:
Brian Gianforcaro 2021-01-01 15:27:42 -08:00 • committed by Andreas Kling
parent bf3772362a
commit 06da50afc7
7 changed files with 124 additions and 13 deletions
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Libraries/LibC/sys/internals.h
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@ -43,5 +43,6 @@ int __cxa_atexit(AtExitFunction exit_function, void* parameter, void* dso_handle
void __cxa_finalize(void* dso_handle);
[[noreturn]] void __cxa_pure_virtual() __attribute__((weak));
[[noreturn]] void __stack_chk_fail();
[[noreturn]] void __stack_chk_fail_local();
__END_DECLS