Re: [PATCH] ipmi: fix unsigned long underflow

From: Corey Minyard
Date: Mon Aug 07 2017 - 08:24:42 EST

On 08/07/2017 03:41 AM, Weilong Chen wrote:
Hi Minyard,

I test this patch, it works.


Thanks, I added a Tested-by: for you and it's queued for the next release.
If it's urgent I can send it in now.

I also added this for the stable kernels 3.16 and later.


On 2017/7/30 10:20, minyard@xxxxxxx wrote:
From: Corey Minyard <cminyard@xxxxxxxxxx>

When I set the timeout to a specific value such as 500ms, the timeout
event will not happen in time due to the overflow in function
ent->timeout -= timeout_period;
if (ent->timeout > 0)

The type of timeout_period is long, but ent->timeout is unsigned long.
This patch makes the type consistent.

Reported-by: Weilong Chen <chenweilong@xxxxxxxxxx>
Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
I like to keep things consistent (though I obviously messed up here)
and keep variables that should be positive unsigned.

But you are right, there is a bug here and some inconsistency.
This patch changes timeout_period to be unsigned and fixes the
check. Can you try this out?

drivers/char/ipmi/ipmi_msghandler.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 810b138..c82d9fd 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -4030,7 +4030,8 @@ smi_from_recv_msg(ipmi_smi_t intf, struct ipmi_recv_msg *recv_msg,

static void check_msg_timeout(ipmi_smi_t intf, struct seq_table *ent,
- struct list_head *timeouts, long timeout_period,
+ struct list_head *timeouts,
+ unsigned long timeout_period,
int slot, unsigned long *flags,
unsigned int *waiting_msgs)
@@ -4043,8 +4044,8 @@ static void check_msg_timeout(ipmi_smi_t intf, struct seq_table *ent,
if (!ent->inuse)

- ent->timeout -= timeout_period;
- if (ent->timeout > 0) {
+ if (timeout_period < ent->timeout) {
+ ent->timeout -= timeout_period;
@@ -4110,7 +4111,8 @@ static void check_msg_timeout(ipmi_smi_t intf, struct seq_table *ent,

-static unsigned int ipmi_timeout_handler(ipmi_smi_t intf, long timeout_period)
+static unsigned int ipmi_timeout_handler(ipmi_smi_t intf,
+ unsigned long timeout_period)
struct list_head timeouts;
struct ipmi_recv_msg *msg, *msg2;