C's specification text around pointer arithmetic is buggy and fails to
account for empty spans. Empty spans are typically represented as
ptr=NULL and len=0, so (T*)NULL + 0 must be defined for ptr + len to
reliably work. C++ does not have this bug and specifies this correctly.
See https://crbug.com/1019588.
This language bug has made its way over to newer versions of UBSan,
which enforce this. In the short term, add bogus length checks as a
workaround. However, unlike the memcpy language bug, we cannot address
this systematically. In the long term, we need to switch libcrypto to
building as C++ for a real fix.
To test this, update our clang revision to that in
https://chromium-review.googlesource.com/c/chromium/src/+/1879890. Note
that clang revision was later reverted in Chromium for seemingly
unrelated reasons.
This newer UBSan also catches a memcpy/OPENSSL_memcpy issue in
siphash.c, from the earlier C NULL bug we'd been working around.
Bug: chromium:1019588, chromium:1019644
Change-Id: I460e547c8cd740db68da8cc2a3a970276ec92e90
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/38584
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
David Benjamin
6be491b7bb