From: Peter Zijlstra Date: Wed, 27 Oct 2010 22:32:58 +0000 (-0700) Subject: mm: fix race in kunmap_atomic() X-Git-Tag: v2.6.37-rc1~85^2~137 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=20273941f2129aa5a432796d98a276ed73d60782;p=pandora-kernel.git mm: fix race in kunmap_atomic() Christoph reported a nice splat which illustrated a race in the new stack based kmap_atomic implementation. The problem is that we pop our stack slot before we're completely done resetting its state -- in particular clearing the PTE (sometimes that's CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear the PTE used for the last slot, that interrupt can reuse the slot in a dirty state, which triggers a BUG in kmap_atomic(). Fix this by introducing kmap_atomic_idx() which reports the current slot index without actually releasing it and use that to find the PTE and delay the _pop() until after we're completely done. Signed-off-by: Peter Zijlstra Reported-by: Christoph Hellwig Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed