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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -fsanitize=safe-stack can prevent -fstack-protector-strong from working sometimes"
href="https://bugs.llvm.org/show_bug.cgi?id=43869">43869</a>
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<th>Summary</th>
<td>-fsanitize=safe-stack can prevent -fstack-protector-strong from working sometimes
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>leonardchan@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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</tr></table>
<p>
<div>
<pre>We ran into an instance where using `-fsanitize=safe-stack
-fstack-protector-strong` does not abort properly as opposed to just using
`-fstack-protector-strong`.
Example:
```
leonardchan@cp-snakewater:~/llvm-monorepo/llvm-build-3-master-fuchsia-toolchain$
cat ~/misc/test.cpp
#include <cstdlib>
#include <cstdio>
#include <cstdint>
#include <string>
#include <string_view>
void write(void *src, size_t len) {
memset(src, rand(), len);
}
std::string change_str(std::string_view str) {
std::string s("__");
return s + str.data();
}
std::string func() {
uint32_t x;
write(&x, 5); // This should be caught since we are writing outside of x
return change_str(std::to_string(x));
}
int main() {
srand(0);
printf("%s\n", func().c_str());
}
leonardchan@cp-snakewater:~/llvm-monorepo/llvm-build-3-master-fuchsia-toolchain$
./install/bin/clang++ ~/misc/test.cpp -fstack-protector-strong -std=c++17
leonardchan@cp-snakewater:~/llvm-monorepo/llvm-build-3-master-fuchsia-toolchain$
./a.out # Aborts as expected
*** stack smashing detected ***: <unknown> terminated
Aborted
leonardchan@cp-snakewater:~/llvm-monorepo/llvm-build-3-master-fuchsia-toolchain$
./install/bin/clang++ ~/misc/test.cpp -fsanitize=safe-stack
-fstack-protector-strong -std=c++17
leonardchan@cp-snakewater:~/llvm-monorepo/llvm-build-3-master-fuchsia-toolchain$
./a.out # No error
__1734829927
```
We abort normally with just `-fstack-protector-strong`, but also adding
`-fsanitize=safe-stack` avoids the abort. I would expect SafeStack and stack
protectors to complement each other rather than one replacing the other.
Not sure if this is related also, but using `-fsanitize=safe-stack` on it's own
still doesn't abort or indicate error.</pre>
</div>
</p>
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