tree 9b2e0f4acb80752d3fe8ffc15bcf1c5bd0b77331
parent 097d80d1abc427ebf8eb6230e5fa2e3a3d96aa69
author Peter Collingbourne <peter@pcc.me.uk> 1574821094 -0800
committer Copybara-Service <copybara-worker@google.com> 1598597778 -0700

scudo: Limit the number of bytes tested in a realloc test.

This test was previously effectively doing:
P = malloc(X); write X bytes to P; P = realloc(P, X - Y); P = realloc(P, X)
and expecting that all X bytes stored to P would still be identical after
the final realloc.

This happens to be true for the current scudo implementation of realloc,
but is not guaranteed to be true by the C standard ("Any bytes in the new
object beyond the size of the old object have indeterminate values.").
This implementation detail will change with the new memory tagging support,
which unconditionally zeros newly allocated granules when memory tagging
is enabled. Fix this by limiting the number of bytes that we test to the
minimum size that we realloc the allocation to.

Differential Revision: https://reviews.llvm.org/D70761

GitOrigin-RevId: b208088a2111aeb805d0984a2ff86b3ce14c725a