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Code Issues Releases Activity

Zero the newly allocated md(4) swap-backed page to prevent random

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kernel memory leakage to userspace. For the typical use, when a
filesystem put on the md disk, the change only results in CPU and
memory bandwidth spent to zero the page, since filsystems make sure
that user never see unwritten content.  But if md disk is used as raw
device by userspace, the garbage is exposed.

Reported by:	Paul Schenkeveld <freebsd@psconsult.nl>
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2012-11-08 03:17:41 +00:00
parent f27de7742d
commit e9f581ba31
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=242744
1 changed files with 9 additions and 0 deletions
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9
sys/dev/md/md.c
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@ -677,6 +677,15 @@ mdstart_swap(struct md_s *sc, struct bio *bp)
sched_unpin();
vm_page_wakeup(m);
break;
} else if (rv == VM_PAGER_FAIL) {
/*
* Pager does not have the page. Zero
* the allocated page, and mark it as
* valid. Do not set dirty, the page
* can be recreated if thrown out.
*/
bzero((void *)sf_buf_kva(sf), PAGE_SIZE);
m->valid = VM_PAGE_BITS_ALL;
}
bcopy((void *)(sf_buf_kva(sf) + offs), p, len);
cpu_flush_dcache(p, len);