From: Chintan Pandya <cpandya@codeaurora.org>
Date: Wed, 6 Aug 2014 23:08:18 +0000 (-0700)
Subject: mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR
X-Git-Tag: v3.17-rc1~94^2~89
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=1d352bfd41e8219cdf9bebe79677700bdc38b540;p=linux.git

mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR

__kmap_atomic_idx is per_cpu variable.  Each CPU can use KM_TYPE_NR
entries from FIXMAP i.e.  from 0 to KM_TYPE_NR - 1.  Allowing
__kmap_atomic_idx to over- shoot to KM_TYPE_NR can mess up with next
CPU's 0th entry which is a bug.  Hence BUG_ON if __kmap_atomic_idx >=
KM_TYPE_NR.

Fix the off-by-on in this test.

Signed-off-by: Chintan Pandya <cpandya@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7fb31da45d03..9286a46b7d69 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -93,7 +93,7 @@ static inline int kmap_atomic_idx_push(void)
 
 #ifdef CONFIG_DEBUG_HIGHMEM
 	WARN_ON_ONCE(in_irq() && !irqs_disabled());
-	BUG_ON(idx > KM_TYPE_NR);
+	BUG_ON(idx >= KM_TYPE_NR);
 #endif
 	return idx;
 }