Subject: Re: [PATCH net] tg3: Avoid NULL pointer dereference in tg3_io_error_detected()

From: "Guilherme G. Piccoli" <[email-masked]>
Date: Tue, 27 Sep 2016 18:27:17 -0300

On 09/27/2016 05:58 PM, Michael Chan wrote:
> On Tue, Sep 27, 2016 at 1:05 PM, Guilherme G. Piccoli
> <[email-masked]> wrote:
>> From: Milton Miller <[email-masked]>
>>
>> While the driver is probing the adapter, an error may occur before the
>> netdev structure is allocated and attached to pci_dev. In this case,
>> not only netdev isn't available, but the tg3 private structure is also
>> not available as it is just math from the NULL pointer, so dereferences
>> must be skipped.
>>
>> The following trace is seen when the error is triggered:
>>
>>    [1.402247] Unable to handle kernel paging request for data at address 0x00001a99
>>    [1.402410] Faulting instruction address: 0xc0000000007e33f8
>>    [1.402450] Oops: Kernel access of bad area, sig: 11 [#1]
>>    [1.402481] SMP NR_CPUS=2048 NUMA PowerNV
>>    [1.402513] Modules linked in:
>>    [1.402545] CPU: 0 PID: 651 Comm: eehd Not tainted 4.4.0-36-generic #55-Ubuntu
>>    [1.402591] task: c000001fe4e42a20 ti: c000001fe4e88000 task.ti: c000001fe4e88000
>>    [1.402742] NIP: c0000000007e33f8 LR: c0000000007e3164 CTR: c000000000595ea0
>>    [1.402787] REGS: c000001fe4e8b790 TRAP: 0300   Not tainted  (4.4.0-36-generic)
>>    [1.402832] MSR: 9000000100009033 <SF,HV,EE,ME,IR,DR,RI,LE>  CR: 28000422  XER: 20000000
>>    [1.403058] CFAR: c000000000008468 DAR: 0000000000001a99 DSISR: 42000000 SOFTE: 1
>>    GPR00: c0000000007e3164 c000001fe4e8ba10 c0000000015c5e00 0000000000000000
>>    GPR04: 0000000000000001 0000000000000000 0000000000000039 0000000000000299
>>    GPR08: 0000000000000000 0000000000000001 c000001fe4e88000 0000000000000006
>>    GPR12: 0000000000000000 c00000000fb40000 c0000000000e6558 c000003ca1bffd00
>>    GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>>    GPR20: 0000000000000000 0000000000000000 0000000000000000 c000000000d52768
>>    GPR24: c000000000d52740 0000000000000100 c000003ca1b52000 0000000000000002
>>    GPR28: 0000000000000900 0000000000000000 c00000000152a0c0 c000003ca1b52000
>>    [1.404226] NIP [c0000000007e33f8] tg3_io_error_detected+0x308/0x340
>>    [1.404265] LR [c0000000007e3164] tg3_io_error_detected+0x74/0x340
>>
>> This patch avoids the NULL pointer dereference by moving the access after
>> the netdev NULL pointer check on tg3_io_error_detected().
>>
>> Fixes: 0486a063b1ff ("tg3: prevent ifup/ifdown during PCI error recovery")
>> Fixes: dfc8f370316b ("net/tg3: Release IRQs on permanent error")
>> Tested-by: Guilherme G. Piccoli <[email-masked]>
>> Signed-off-by: Milton Miller <[email-masked]>
>> Signed-off-by: Guilherme G. Piccoli <[email-masked]>
>
> Looks good.  Do we need to add !netdev check in tg3_io_resume()?

Thanks Michael. It's a good point - I didn't trigger any error without 
the check, but looking at error handlers, every one seems to have this 
check except tg3_io_resume().

Do you want us to send a v2 including this check? Or maybe another patch?

Cheers,

Guilherme