linux-kernel - [PATCH 1/2] ras: fix an off-by-one error in __find

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Message-Id: <20190416012001.5338-1-xiyou.wangcong@gmail.com>
Date:   Mon, 15 Apr 2019 18:20:00 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-edac@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>,
        Tony Luck <tony.luck@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 1/2] ras: fix an off-by-one error in __find_elem()

ce_arr.array[] is always within the range [0, ce_arr.n-1].
However, the binary search code in __find_elem() uses ce_arr.n
as the maximum index, which could lead to an off-by-one
out-of-bound access when the element after the last is exactly
the one just got deleted, that is, 'min' returned to caller as
'ce_arr.n'.

Fixes: 011d82611172 ("RAS: Add a Corrected Errors Collector")
Cc: Tony Luck <tony.luck@...el.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 drivers/ras/cec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 2d9ec378a8bc..61332c9aab5a 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -184,7 +184,7 @@ static void cec_timer_fn(struct timer_list *unused)
 static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to)
 {
 	u64 this_pfn;
-	int min = 0, max = ca->n;
+	int min = 0, max = ca->n - 1;
 
 	while (min < max) {
 		int tmp = (max + min) >> 1;
-- 
2.20.1