The variable ioc->taskmgmt_quiesce_io is often protected by the lock
ioc->taskmgmt_lock when is accessed. Here is an example in
mpt_SoftResetHandler():
spin_lock_irqsave(&ioc->taskmgmt_lock, flags);
...
ioc->taskmgmt_quiesce_io = 0;
...
spin_unlock_irqrestore(&ioc->taskmgmt_lock, flags);
However, ioc->taskmgmt_quiesce_io is set to 1 without holding the lock
ioc->taskmgmt_lock in mpt_ioc_reset():
case MPT_IOC_SETUP_RESET:
ioc->taskmgmt_quiesce_io = 1;
In my opinion, this may be a harmful race, because the value of
ioc->taskmgmt_quiesce_io can be rewritten by mpt_ioc_reset() when
another thread is accessing it.
To fix this possible data race, a lock and unlock pair is added when
accessing the variable ioc->taskmgmt_quiesce_io.
Reported-by: BassCheck <[email protected]>
Signed-off-by: Tuo Li <[email protected]>
---
drivers/message/fusion/mptbase.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/message/fusion/mptbase.c b/drivers/message/fusion/mptbase.c
index 4bf669c55649..86d7b4defeb0 100644
--- a/drivers/message/fusion/mptbase.c
+++ b/drivers/message/fusion/mptbase.c
@@ -6561,9 +6561,12 @@ mpt_config(MPT_ADAPTER *ioc, CONFIGPARMS *pCfg)
static int
mpt_ioc_reset(MPT_ADAPTER *ioc, int reset_phase)
{
+ unsigned long flags;
switch (reset_phase) {
case MPT_IOC_SETUP_RESET:
+ spin_lock_irqsave(&ioc->taskmgmt_lock, flags);
ioc->taskmgmt_quiesce_io = 1;
+ spin_unlock_irqrestore(&ioc->taskmgmt_lock, flags);
dtmprintk(ioc, printk(MYIOC_s_DEBUG_FMT
"%s: MPT_IOC_SETUP_RESET\n", ioc->name, __func__));
break;
--
2.34.1
On 10/24/23 00:27, Tuo Li wrote:
> In my opinion, this may be a harmful race, because the value of
> ioc->taskmgmt_quiesce_io can be rewritten by mpt_ioc_reset() when
> another thread is accessing it.
It is a common pattern in the Linux kernel that a variable is set from
one thread without using locking and is read by another thread that is
holding a lock. It should be sufficient here to use WRITE_ONCE(). I
don't think that acquiring and releasing the spin lock is required.
Thanks,
Bart.