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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - shadow stack not reserved for 64-bit ms_abi function pointer with optimization on"
href="http://llvm.org/bugs/show_bug.cgi?id=22709">22709</a>
</td>
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<tr>
<th>Summary</th>
<td>shadow stack not reserved for 64-bit ms_abi function pointer with optimization on
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.4
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dlehman@esri.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=13948" name="attach_13948" title="test case with instructions">attachment 13948</a> <a href="attachment.cgi?id=13948&action=edit" title="test case with instructions">[details]</a></span>
test case with instructions
a shadow stack is not reserved for a function pointer with the ms_abi attribute
on 64-bit when optimization is turned on. the function called then can
overwrite the caller's stack, causing a crash
test case is attached but is very simple:
typedef int (*__attribute__((ms_abi)) callback_t)(int);
int wrapper(callback_t cb, int arg)
{
return (*cb)(arg);
}
when compiled with 'clang case.c -O2 -c' the result is:
0000000000000000 <wrapper>:
0: 89 f1 mov %esi,%ecx <- correct register for ms_abi
2: ff e7 jmpq *%rdi <- but no 32-byte shadow stack
a stack is reserved if optimization is disabled:
0000000000000000 <wrapper>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 48 83 ec 30 sub $0x30,%rsp
8: 48 89 7d f8 mov %rdi,-0x8(%rbp)
c: 89 75 f4 mov %esi,-0xc(%rbp)
f: 48 8b 7d f8 mov -0x8(%rbp),%rdi
13: 8b 4d f4 mov -0xc(%rbp),%ecx
16: ff d7 callq *%rdi
18: 48 83 c4 30 add $0x30,%rsp
1c: 5d pop %rbp
1d: c3 retq
stack space is reserved for straight function calls. seems to be just an issue
for function pointers
found with 3.4.1 but also happens with 3.5.1</pre>
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