Re: [PATCH] pinctrl: at91: fix null pointer dereference

[Jean-Christophe PLAGNIOL-VILLARD]

> On Jul 13, 2015, at 9:00 PM, Ludovic Desroches <ludovic.desroches@xxxxxxxxx> wrote:
> 
> On Mon, Jul 13, 2015 at 02:14:51PM +0800, Jean-Christophe PLAGNIOL-VILLARD wrote:
>> 
>>> On Jul 3, 2015, at 12:06 AM, David Dueck <davidcdueck@xxxxxxxxxxxxxx> wrote:
>>> 
>>> Not all gpio banks are necessarily enabled, in the current code this can
>>> lead to null pointer dereferences.
>>> 
>>> [   51.130000] Unable to handle kernel NULL pointer dereference at virtual address 00000058
>>> [   51.130000] pgd = dee04000
>>> [   51.130000] [00000058] *pgd=3f66d831, *pte=00000000, *ppte=00000000
>>> [   51.140000] Internal error: Oops: 17 [#1] ARM
>>> [   51.140000] Modules linked in:
>>> [   51.140000] CPU: 0 PID: 1664 Comm: cat Not tainted 4.1.1+ #6
>>> [   51.140000] Hardware name: Atmel SAMA5
>>> [   51.140000] task: df6dd880 ti: dec60000 task.ti: dec60000
>>> [   51.140000] PC is at at91_pinconf_get+0xb4/0x200
>>> [   51.140000] LR is at at91_pinconf_get+0xb4/0x200
>>> [   51.140000] pc : [<c01e71a0>]    lr : [<c01e71a0>]    psr: 600f0013
>>> sp : dec61e48  ip : 600f0013  fp : df522538
>>> [   51.140000] r10: df52250c  r9 : 00000058  r8 : 00000068
>>> [   51.140000] r7 : 00000000  r6 : df53c910  r5 : 00000000  r4 : dec61e7c
>>> [   51.140000] r3 : 00000000  r2 : c06746d4  r1 : 00000000  r0 : 00000003
>>> [   51.140000] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>>> [   51.140000] Control: 10c53c7d  Table: 3ee04059  DAC: 00000015
>>> [   51.140000] Process cat (pid: 1664, stack limit = 0xdec60208)
>>> [   51.140000] Stack: (0xdec61e48 to 0xdec62000)
>>> [   51.140000] 1e40:                   00000358 00000000 df522500 ded15f80 c05a9d08 ded15f80
>>> [   51.140000] 1e60: 0000048c 00000061 df522500 ded15f80 c05a9d08 c01e7304 ded15f80 00000000
>>> [   51.140000] 1e80: c01e6008 00000060 0000048c c01e6034 c01e5f6c ded15f80 dec61ec0 00000000
>>> [   51.140000] 1ea0: 00020000 ded6f280 dec61f80 00000001 00000001 c00ae0b8 b6e80000 ded15fb0
>>> [   51.140000] 1ec0: 00000000 00000000 df4bc974 00000055 00000800 ded6f280 b6e80000 ded6f280
>>> [   51.140000] 1ee0: ded6f280 00020000 b6e80000 00000000 00020000 c0090dec c0671e1c dec61fb0
>>> [   51.140000] 1f00: b6f8b510 00000001 00004201 c000924c 00000000 00000003 00000003 00000000
>>> [   51.140000] 1f20: df4bc940 00022000 00000022 c066e188 b6e7f000 c00836f4 000b6e7f ded6f280
>>> [   51.140000] 1f40: ded6f280 b6e80000 dec61f80 ded6f280 00020000 c0091508 00000000 00000003
>>> [   51.140000] 1f60: 00022000 00000000 00000000 ded6f280 ded6f280 00020000 b6e80000 c0091d9c
>>> [   51.140000] 1f80: 00000000 00000000 ffffffff 00020000 00020000 b6e80000 00000003 c000f124
>>> [   51.140000] 1fa0: dec60000 c000efa0 00020000 00020000 00000003 b6e80000 00020000 000271c4
>>> [   51.140000] 1fc0: 00020000 00020000 b6e80000 00000003 7fffe000 00000000 00000000 00020000
>>> [   51.140000] 1fe0: 00000000 bef50b64 00013835 b6f29c76 400f0030 00000003 00000000 00000000
>>> [   51.140000] [<c01e71a0>] (at91_pinconf_get) from [<c01e7304>] (at91_pinconf_dbg_show+0x18/0x2c0)
>>> [   51.140000] [<c01e7304>] (at91_pinconf_dbg_show) from [<c01e6034>] (pinconf_pins_show+0xc8/0xf8)
>>> [   51.140000] [<c01e6034>] (pinconf_pins_show) from [<c00ae0b8>] (seq_read+0x1a0/0x464)
>>> [   51.140000] [<c00ae0b8>] (seq_read) from [<c0090dec>] (__vfs_read+0x20/0xd0)
>>> [   51.140000] [<c0090dec>] (__vfs_read) from [<c0091508>] (vfs_read+0x7c/0x108)
>>> [   51.140000] [<c0091508>] (vfs_read) from [<c0091d9c>] (SyS_read+0x40/0x94)
>>> [   51.140000] [<c0091d9c>] (SyS_read) from [<c000efa0>] (ret_fast_syscall+0x0/0x3c)
>>> [   51.140000] Code: eb010ec2 e30a0d08 e34c005a eb0ae5a7 (e5993000)
>>> [   51.150000] ---[ end trace fb3c370da3ea4794 ]---
>>> 
>>> Signed-off-by: David Dueck <davidcdueck@xxxxxxxxxxxxxx>
>>> CC: Nicolas Ferre <nicolas.ferre@xxxxxxxxx>
>>> CC: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
>>> CC: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
>>> CC: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
>>> CC: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>> CC: linux-kernel@xxxxxxxxxxxxxxx
>>> ---
>>> drivers/pinctrl/pinctrl-at91.c | 15 +++++++++++++++
>>> 1 file changed, 15 insertions(+)
>>> 
>>> diff --git a/drivers/pinctrl/pinctrl-at91.c b/drivers/pinctrl/pinctrl-at91.c
>>> index a082447..2deb130 100644
>>> --- a/drivers/pinctrl/pinctrl-at91.c
>>> +++ b/drivers/pinctrl/pinctrl-at91.c
>>> @@ -320,6 +320,9 @@ static const struct pinctrl_ops at91_pctrl_ops = {
>>> static void __iomem *pin_to_controller(struct at91_pinctrl *info,
>>> 				 unsigned int bank)
>>> {
>>> +	if (!gpio_chips[bank])
>>> +		return NULL;
>> 
>> if the bank is not enabled you should never arrived here
> 
> But you can because in pinconf_pins_show you have:
> for (i = 0; i < pctldev->desc->npins; i++)
> 
> And in the pinctrl-at91 driver you have:
> at91_pinctrl_desc.npins = gpio_banks * MAX_NB_GPIO_PER_BANK;
> 
>> 
>> 
>>> +
>>> 	return gpio_chips[bank]->regbase;
>>> }
>>> 
>>> @@ -729,6 +732,10 @@ static int at91_pmx_set(struct pinctrl_dev *pctldev, unsigned selector,
>>> 		pin = &pins_conf[i];
>>> 		at91_pin_dbg(info->dev, pin);
>>> 		pio = pin_to_controller(info, pin->bank);
>>> +
>>> +		if (!pio)
>>> +			continue;
>>> +
>> 
>> or here
>>> 		mask = pin_to_mask(pin->pin);
>>> 		at91_mux_disable_interrupt(pio, mask);
>>> 		switch (pin->mux) {
>>> @@ -848,6 +855,10 @@ static int at91_pinconf_get(struct pinctrl_dev *pctldev,
>>> 	*config = 0;
>>> 	dev_dbg(info->dev, "%s:%d, pin_id=%d", __func__, __LINE__, pin_id);
>>> 	pio = pin_to_controller(info, pin_to_bank(pin_id));
>>> +
>>> +	if (!pio)
>>> +		return -EINVAL;
>>> +
>> ditto
>>> 	pin = pin_id % MAX_NB_GPIO_PER_BANK;
>>> 
>>> 	if (at91_mux_get_multidrive(pio, pin))
>>> @@ -889,6 +900,10 @@ static int at91_pinconf_set(struct pinctrl_dev *pctldev,
>>> 			"%s:%d, pin_id=%d, config=0x%lx",
>>> 			__func__, __LINE__, pin_id, config);
>>> 		pio = pin_to_controller(info, pin_to_bank(pin_id));
>>> +
>>> +		if (!pio)
>>> +			return -EINVAL;
>>> +
>> 
>> ditoo
>> 
>> NACK
>> 
>> the problem is somewhere else
> 
> I agree that the root cause is somewhere else.

So we MUST fix the root and not do quick fix

> We have a
> 'gpio_chips[MAX_GPIO_BANKS]' table and 'npins = gpio_banks *
> MAX_NB_GPIO_PER_BANK' where 'gpio_banks = max(gpio_banks, alias_idx +
> 1)'. If you have a disabled controller, you will have a NULL pointer in
> the gpio_chips table and some pins which can't be accessed (for example
> because this pio controller is secure only).

I agree but you to catch in one point ONLY of the bank is enabled or not
not everywhere.

> 
> This patch is a sanity check.

You need only one at the entry point if you do have a NULL pointer accessed by the code
path the kernel need to oops so you known there is a problem, specially in secure mode.
This could means a bug or worse.

And This will cause CPU cycle consuming for nothing.

> It is a bit rude to nack this kind of
> patch telling we should never get this situation. There is always some
> cases we didn't think of. Moreover, I think this patch is in the view of
> the driver: the device can manage up to 160 pins but for some reasons, only
> 128 can be managed by Linux.

This an other issue.
> 
> 
>> 
>> Best Regards,
>> J.
>>> 		pin = pin_id % MAX_NB_GPIO_PER_BANK;
>>> 		mask = pin_to_mask(pin);
>>> 
>>> -- 
>>> 2.4.4
>>> 
>> 
> 
> Regards
> 
> Ludovic

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