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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - UBsan warns on access to 0 sized arrays in union"
href="https://bugs.llvm.org/show_bug.cgi?id=44608">44608</a>
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<th>Summary</th>
<td>UBsan warns on access to 0 sized arrays in union
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>manojgupta@google.com
</td>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<pre>Copied from Chrome OS bug
<a href="https://bugs.chromium.org/p/chromium/issues/detail?id=1043405">https://bugs.chromium.org/p/chromium/issues/detail?id=1043405</a>
One of the programs in Chrome OS uses a 0 sized array inside a union.
ubsan errors on oob accesses to this member. Given that this array is 0 sized,
should accesses to it be treated differently?
Relevant struct snippet from
<a href="https://chromium.git.corp.google.com/chromiumos/platform/vboot_reference/+/f5367d598a985520a8c935f68ac90d295c7b8d8e/firmware/2lib/include/2sha.h">https://chromium.git.corp.google.com/chromiumos/platform/vboot_reference/+/f5367d598a985520a8c935f68ac90d295c7b8d8e/firmware/2lib/include/2sha.h</a>
struct vb2_hash {
/* enum vb2_hash_algorithm. Fixed width for serialization.
Single byte to avoid endianness issues. */
uint8_t algo;
/* Padding to align and to match existing CBFS attribute. */
uint8_t reserved[3];
/* The actual digest. Can add new types here as required. */
union {
uint8_t raw[0]; // triggers ubsan oob checks
#if VB2_SUPPORT_SHA1
uint8_t sha1[VB2_SHA1_DIGEST_SIZE];
#endif
#if VB2_SUPPORT_SHA256
uint8_t sha256[VB2_SHA256_DIGEST_SIZE];
#endif
#if VB2_SUPPORT_SHA512
uint8_t sha512[VB2_SHA512_DIGEST_SIZE];
#endif
} bytes; /* This has a name so that it's easy to sizeof(). */
};</pre>
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