https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=215209
--- Comment #9 from commit-h...@freebsd.org --- A commit references this bug: Author: dim Date: Sun Dec 18 14:31:12 UTC 2016 New revision: 310228 URL: https://svnweb.freebsd.org/changeset/base/310228 Log: MFC r310013 (by cperciva): 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. MFC r310086: In xbd_connect(), use correct scanf conversion specifiers for the feature_barrier and feature_flush variables. Otherwise, adjacent variables on the stack, such as sector_size, may be overwritten, with disastrous results. Note that I did not see a good reason to revert the addition of zero checks introduced in r310013. Better safe than sorry. PR: 215209 Tested by: royger Changes: _U stable/10/ stable/10/sys/dev/xen/blkfront/blkfront.c _U stable/11/ stable/11/sys/dev/xen/blkfront/blkfront.c _U stable/9/ _U stable/9/sys/ stable/9/sys/dev/xen/blkfront/blkfront.c -- You are receiving this mail because: You are on the CC list for the bug. You are the assignee for the bug. _______________________________________________ freebsd-xen@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-xen To unsubscribe, send any mail to "freebsd-xen-unsubscr...@freebsd.org"