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| /freebsd/sys/dev/xen/blkfront/ |
| H A D | blkfront.c | diff 93954c2da374f8fff6376fbf1f2e1c60a22453ed Tue Dec 13 07:54:13 CET 2016 Colin Percival <cperciva@FreeBSD.org> 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.
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