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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 - Segmentation fault triggered by calling dlsym() with a null pointer in interceptor machinery"
href="https://bugs.llvm.org/show_bug.cgi?id=49486">49486</a>
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<th>Summary</th>
<td>Segmentation fault triggered by calling dlsym() with a null pointer in interceptor machinery
</td>
</tr>
<tr>
<th>Product</th>
<td>compiler-rt
</td>
</tr>
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<th>Version</th>
<td>unspecified
</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>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>compiler-rt
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>aanderso@tcd.ie
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<p>
<div>
<pre>A segmentation fault is triggered when the compiler-rt calls dlsym() with a
null pointer at compiler-rt/lib/interception/interception_linux.cpp:42
Repro:
In a sanitizer, attempt to intercept calls to malloc like so:
INTERCEPTOR(void*, malloc, uptr size) {
return REAL(malloc)(size);
}
At the point where we call INTERCEPT_FUNCTION(malloc), a segmentation fault is
triggered with the following backtrace:
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff7e23c38 in ?? () from /usr/lib/libdl.so.2
#2 0x00007ffff7e23520 in dlsym () from /usr/lib/libdl.so.2
#3 0x0000000000409bd4 in GetFuncAddr () at
/home/andrew/Workspaces/asan-workspace/llvm-project-sanitizer-demo/compiler-rt/lib/interception/interception_linux.cpp:42
#4 InterceptFunction () at
/home/andrew/Workspaces/asan-workspace/llvm-project-sanitizer-demo/compiler-rt/lib/interception/interception_linux.cpp:61
#5 0x0000000000409392 in __gsan::InitializeInterceptors() () at
/home/andrew/Workspaces/asan-workspace/llvm-project-sanitizer-demo/compiler-rt/lib/gsan/gsan_interceptors.cpp:536
#6 0x00000000004045a9 in __gsan_init () at
/home/andrew/Workspaces/asan-workspace/llvm-project-sanitizer-demo/compiler-rt/lib/gsan/gsan.cpp:106
#7 0x00007ffff7fdbfce in _dl_init () from /lib64/ld-linux-x86-64.so.2
#8 0x00007ffff7fcd0ca in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
#9 0x0000000000000001 in ?? ()
#10 0x00007fffffffea03 in ?? ()
#11 0x0000000000000000 in ?? ()
Upon inspection, it can be seen that the const char* name that GetFuncAddr() is
passed at compiler-rt/lib/interception/interception_linux.cpp:42 is null. This
is surprising, because the const char* "malloc" is not null.
Building with a checkout of main from the LLVM github monorepo. I have not
touched anything in the compiler-rt, but I'm just trying to add my own
customized sanitizer. It is fairly simple, and just makes use of facilities
already present in the compiler-rt.</pre>
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