2010-04-16 11:57:00

by Phil Carmody

Subject: [PATCH] mfd: Fix fencepost error in reg cache access check

From: Phil Carmody <[email protected]>

Accessing num_reg elements in the interval [reg .. reg+num_regs)
is permitted if (reg+numregs <= array size), so barf when that
excluded upper bound is > array size. The prior -1 would give
access to one too many elements.

Signed-off-by: Phil Carmody <[email protected]>
---
drivers/mfd/wm8400-core.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/wm8400-core.c b/drivers/mfd/wm8400-core.c
index 865ce01..e08aafa 100644
--- a/drivers/mfd/wm8400-core.c
+++ b/drivers/mfd/wm8400-core.c
@@ -118,7 +118,7 @@ static int wm8400_read(struct wm8400 *wm8400, u8 reg, int num_regs, u16 *dest)
{
int i, ret = 0;

- BUG_ON(reg + num_regs - 1 > ARRAY_SIZE(wm8400->reg_cache));
+ BUG_ON(reg + num_regs > ARRAY_SIZE(wm8400->reg_cache));

/* If there are any volatile reads then read back the entire block */
for (i = reg; i < reg + num_regs; i++)
@@ -144,7 +144,7 @@ static int wm8400_write(struct wm8400 *wm8400, u8 reg, int num_regs,
{
int ret, i;

- BUG_ON(reg + num_regs - 1 > ARRAY_SIZE(wm8400->reg_cache));
+ BUG_ON(reg + num_regs > ARRAY_SIZE(wm8400->reg_cache));

for (i = 0; i < num_regs; i++) {
BUG_ON(!reg_data[reg + i].writable);
--
1.6.0.4

2010-04-16 18:50:01

by Mark Brown

Subject: Re: [PATCH] mfd: Fix fencepost error in reg cache access check

On Fri, Apr 16, 2010 at 03:00:09PM +0300, Phil Carmody wrote:
> From: Phil Carmody <[email protected]>
>
> Accessing num_reg elements in the interval [reg .. reg+num_regs)
> is permitted if (reg+numregs <= array size), so barf when that
> excluded upper bound is > array size. The prior -1 would give
> access to one too many elements.

Acked-by: Mark Brown <[email protected]>