[Bug 215209] Kernel panic at boot under XEN: integer divide fault while in kernel mode
bugzilla-noreply at freebsd.org
bugzilla-noreply at freebsd.org
Tue Dec 13 06:54:37 UTC 2016
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215209
--- Comment #7 from commit-hook at freebsd.org ---
A commit references this bug:
Author: cperciva
Date: Tue Dec 13 06:54:14 UTC 2016
New revision: 310013
URL: https://svnweb.freebsd.org/changeset/base/310013
Log:
Check that blkfront devices have a non-zero number of sectors and a
non-zero sector size. Such a device would be a virtual disk of zero
bytes; clearly not useful, and not something we should try to attach.
As a fortuitous side effect, checking that these values are non-zero
here results in them not *becoming* zero later on the function. This
odd behaviour began with r309124 (clang 3.9.0) but is challenging to
debug; making any changes to this function whatsoever seems to affect
the llvm optimizer behaviour enough to make the unexpected zeroing of
the sector_size variable cease.
PR: 215209
Security: The potential for variables to unexpectedly become zero
has worrying consequences for security in general, but
not so much in this particular context.
Changes:
head/sys/dev/xen/blkfront/blkfront.c
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