> > > This suggests that initialization may be attempted more than once. The key cache
> > > is allocated only once, but the number of keys is read for each attempt.
> > >
> > > No idea if that can happen, but if the number of keys can increase after
> > > the first initialization attempt you would have an explanation for the crash.
> >
> > Good idea, and easy enough to test with the patch below.
> >
> Should we apply this patch even though it may not solve the specific problem ?
Yes, why not - it certainly won't hurt. I am running it right now, so
it is at least run-tested.
> Again, not sure if the key count can change, but the current code is at the very
> least inconsistent, as it keeps reading the key count without updating or
> verifying the cache size.
Yes - I agree that the error state is far-fetched, but it is hard to
see any other logical explanation. There is of course always the
possibility that the problem is somewhere else completely.
Proper patch attached.
Thanks,
Henrik
---
>From dedefba9167913c46e1896ce0624e68ffe95d532 Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@xxxxxxxxxxx>
Date: Thu, 26 Sep 2013 08:33:16 +0200
Subject: [PATCH] hwmon: (applesmc) Check key count before proceeding
After reports from Chris and Josh Boyer of a rare crash in applesmc,
Guenter pointed at the initialization problem fixed below. The patch
has not been verified to fix the crash, but should be applied
regardless.
Reported-by: <jwboyer@xxxxxxxxxxxxxxxxx>
Suggested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Henrik Rydberg <rydberg@xxxxxxxxxxx>
---
drivers/hwmon/applesmc.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 62c2e32..98814d1 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -525,16 +525,25 @@ static int applesmc_init_smcreg_try(void)
{
struct applesmc_registers *s = &smcreg;
bool left_light_sensor, right_light_sensor;
+ unsigned int count;
u8 tmp[1];
int ret;
if (s->init_complete)
return 0;
- ret = read_register_count(&s->key_count);
+ ret = read_register_count(&count);
if (ret)
return ret;
+ if (s->cache && s->key_count != count) {
+ pr_warn("key count changed from %d to %d\n",
+ s->key_count, count);
+ kfree(s->cache);
+ s->cache = NULL;
+ }
+ s->key_count = count;
+
if (!s->cache)
s->cache = kcalloc(s->key_count, sizeof(*s->cache), GFP_KERNEL);
if (!s->cache)
--
1.8.3.4
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