Re: [PATCH] hwmon: (nct6775) Fix crash in clear_caseopen

[Denis Pauk <pauk.denis@gmail.com>]

On Mon, 24 Jan 2022 14:32:26 -0800
Guenter Roeck <linux@roeck-us.net> wrote:

> On 1/24/22 14:21, Denis Pauk wrote:
> > On Sun, 23 Jan 2022 18:32:48 -0800
> > Guenter Roeck <linux@roeck-us.net> wrote:
> >   
> >> Paweł Marciniak reports the following crash, observed when clearing
> >> the chassis intrusion alarm.
> >>
> >> BUG: kernel NULL pointer dereference, address: 0000000000000028
> >> PGD 0 P4D 0
> >> Oops: 0000 [#1] PREEMPT SMP PTI
> >> CPU: 3 PID: 4815 Comm: bash Tainted: G S
> >> 5.16.2-200.fc35.x86_64 #1 Hardware name: To Be Filled By O.E.M. To
> >> Be Filled By O.E.M./Z97 Extreme4, BIOS P2.60A 05/03/2018 RIP:
> >> 0010:clear_caseopen+0x5a/0x120 [nct6775] Code: 68 70 e8 e9 32 b1 e3
> >> 85 c0 0f 85 d2 00 00 00 48 83 7c 24 ... RSP: 0018:ffffabcb02803dd8
> >> EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000002 RCX:
> >> 0000000000000000 RDX: ffff8e8808192880 RSI: 0000000000000000 RDI:
> >> ffff8e87c7509a68 RBP: 0000000000000000 R08: 0000000000000001 R09:
> >> 000000000000000a R10: 000000000000000a R11: f000000000000000 R12:
> >> 000000000000001f R13: ffff8e87c7509828 R14: ffff8e87c7509a68 R15:
> >> ffff8e88494527a0 FS:  00007f4db9151740(0000)
> >> GS:ffff8e8ebfec0000(0000) knlGS:0000000000000000 CS:  0010 DS: 0000
> >> ES: 0000 CR0: 0000000080050033 CR2: 0000000000000028 CR3:
> >> 0000000166b66001 CR4: 00000000001706e0 Call Trace:
> >>   <TASK>
> >>   kernfs_fop_write_iter+0x11c/0x1b0
> >>   new_sync_write+0x10b/0x180
> >>   vfs_write+0x209/0x2a0
> >>   ksys_write+0x4f/0xc0
> >>   do_syscall_64+0x3b/0x90
> >>   entry_SYSCALL_64_after_hwframe+0x44/0xae
> >>
> >> The problem is that the device passed to clear_caseopen() is the
> >> hwmon device, not the platform device, and the platform data is
> >> not set in the hwmon device. Store the pointer to sio_data in
> >> struct nct6775_data and get if from there if needed.
> >>
> >> Fixes: 2e7b9886968b ("hwmon: (nct6775) Use superio_*() function
> >> pointers in sio_data.") Cc: Denis Pauk <pauk.denis@gmail.com>
> >> Cc: Bernhard Seibold <mail@bernhard-seibold.de>
> >> Reported-by: Paweł Marciniak <pmarciniak@lodz.home.pl>
> >> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> >> ---
> >>   drivers/hwmon/nct6775.c | 6 +++---
> >>   1 file changed, 3 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
> >> index fd3f91cb01c6..098d12b9ecda 100644
> >> --- a/drivers/hwmon/nct6775.c
> >> +++ b/drivers/hwmon/nct6775.c
> >> @@ -1175,7 +1175,7 @@ static inline u8 in_to_reg(u32 val, u8 nr)
> >>   
> >>   struct nct6775_data {
> >>   	int addr;	/* IO base of hw monitor block */
> >> -	int sioreg;	/* SIO register address */
> >> +	struct nct6775_sio_data *sio_data;
> >>   	enum kinds kind;  
> > What do you think about remove kind field also from struct
> > nct6775_data? Code has copy of this field inside of the struct
> > nct6775_sio_data.  
> 
> I thought about it, but it would add a level of indirection to
> each access, and it is used for each register access (through
> is_word_sized). That would make the change pretty expensive
> in terms of runtime cost.
> 

I see, thank you.

> Guenter
> 
> >>   	const char *name;
> >>   
> >> @@ -3559,7 +3559,7 @@ clear_caseopen(struct device *dev, struct
> >> device_attribute *attr, const char *buf, size_t count)
> >>   {
> >>   	struct nct6775_data *data = dev_get_drvdata(dev);
> >> -	struct nct6775_sio_data *sio_data = dev_get_platdata(dev);
> >> +	struct nct6775_sio_data *sio_data = data->sio_data;
> >>   	int nr = to_sensor_dev_attr(attr)->index -
> >> INTRUSION_ALARM_BASE; unsigned long val;
> >>   	u8 reg;
> >> @@ -3967,7 +3967,7 @@ static int nct6775_probe(struct
> >> platform_device *pdev) return -ENOMEM;
> >>   
> >>   	data->kind = sio_data->kind;
> >> -	data->sioreg = sio_data->sioreg;
> >> +	data->sio_data = sio_data;
> >>   
> >>   	if (sio_data->access == access_direct) {
> >>   		data->addr = res->start;  
> > 
> > Tested-by: Denis Pauk <pauk.denis@gmail.com>
> > 
> > Best regards,
> >               Denis.  
> 



Best regards,
             Denis.