From: Linus Torvalds <torvalds@woody.osdl.org>
Date: Sat, 16 Dec 2006 17:44:32 +0000 (-0800)
Subject: Fix incorrect user space access locking in mincore()
X-Git-Tag: v2.6.20-rc2~125
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2f77d107050abc14bc393b34bdb7b91cf670c250;p=pandora-kernel.git

Fix incorrect user space access locking in mincore()

Doug Chapman noticed that mincore() will doa "copy_to_user()" of the
result while holding the mmap semaphore for reading, which is a big
no-no.  While a recursive read-lock on a semaphore in the case of a page
fault happens to work, we don't actually allow them due to deadlock
schenarios with writers due to fairness issues.

Doug and Marcel sent in a patch to fix it, but I decided to just rewrite
the mess instead - not just fixing the locking problem, but making the
code smaller and (imho) much easier to understand.

Cc: Doug Chapman <dchapman@redhat.com>
Cc: Marcel Holtmann <holtmann@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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