Hi John,
> On Feb 13, 2018, at 2:54 AM, John Garry <john.garry@xxxxxxxxxx> wrote:
>
> On 12/02/2018 18:28, Himanshu Madhani wrote:
>> This patch fixes NULL pointer crash due to active timer running
>> for abort IOCB.
>>
>>> From crash dump analysis it was discoverd that get_next_timer_interrupt()
>> encountered a corrupted entry on the timer list.
>>
>> #9 [ffff95e1f6f0fd40] page_fault at ffffffff914fe8f8
>> [exception RIP: get_next_timer_interrupt+440]
>> RIP: ffffffff90ea3088 RSP: ffff95e1f6f0fdf0 RFLAGS: 00010013
>> RAX: ffff95e1f6451028 RBX: 000218e2389e5f40 RCX: 00000001232ad600
>> RDX: 0000000000000001 RSI: ffff95e1f6f0fdf0 RDI: 0000000001232ad6
>> RBP: ffff95e1f6f0fe40 R8: ffff95e1f6451188 R9: 0000000000000001
>> R10: 0000000000000016 R11: 0000000000000016 R12: 00000001232ad5f6
>> R13: ffff95e1f6450000 R14: ffff95e1f6f0fdf8 R15: ffff95e1f6f0fe10
>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
>>
>> Looking at the assembly of get_next_timer_interrupt(), address came
>> from %r8 (ffff95e1f6451188) which is pointing to list_head with single
>> entry at ffff95e5ff621178.
>>
>> 0xffffffff90ea307a <get_next_timer_interrupt+426>: mov (%r8),%rdx
>> 0xffffffff90ea307d <get_next_timer_interrupt+429>: cmp %r8,%rdx
>> 0xffffffff90ea3080 <get_next_timer_interrupt+432>: je 0xffffffff90ea30a7 <get_next_timer_interrupt+471>
>> 0xffffffff90ea3082 <get_next_timer_interrupt+434>: nopw 0x0(%rax,%rax,1)
>> 0xffffffff90ea3088 <get_next_timer_interrupt+440>: testb $0x1,0x18(%rdx)
>>
>> crash> rd ffff95e1f6451188 10
>> ffff95e1f6451188: ffff95e5ff621178 ffff95e5ff621178 x.b.....x.b.....
>> ffff95e1f6451198: ffff95e1f6451198 ffff95e1f6451198 ..E.......E.....
>> ffff95e1f64511a8: ffff95e1f64511a8 ffff95e1f64511a8 ..E.......E.....
>> ffff95e1f64511b8: ffff95e77cf509a0 ffff95e77cf509a0 ...|.......|....
>> ffff95e1f64511c8: ffff95e1f64511c8 ffff95e1f64511c8 ..E.......E.....
>>
>> crash> rd ffff95e5ff621178 10
>> ffff95e5ff621178: 0000000000000001 ffff95e15936aa00 ..........6Y....
>> ffff95e5ff621188: 0000000000000000 00000000ffffffff ................
>> ffff95e5ff621198: 00000000000000a0 0000000000000010 ................
>> ffff95e5ff6211a8: ffff95e5ff621198 000000000000000c ..b.............
>> ffff95e5ff6211b8: 00000f5800000000 ffff95e751f8d720 ....X... ..Q....
>>
>> ffff95e5ff621178 belongs to freed mempool object at ffff95e5ff621080.
>>
>> CACHE NAME OBJSIZE ALLOCATED TOTAL SLABS SSIZE
>> ffff95dc7fd74d00 mnt_cache 384 19785 24948 594 16k
>> SLAB MEMORY NODE TOTAL ALLOCATED FREE
>> ffffdc5dabfd8800 ffff95e5ff620000 1 42 29 13
>> FREE / [ALLOCATED]
>> ffff95e5ff621080 (cpu 6 cache)
>>
>> Examining the contents of that memory reveals a pointer to a constant
>> string in the driver, "abort\0", which is set by qla24xx_async_abort_cmd().
>>
>> crash> rd ffffffffc059277c 20
>> ffffffffc059277c: 6e490074726f6261 0074707572726574 abort.Interrupt.
>> ffffffffc059278c: 00676e696c6c6f50 6920726576697244 Polling.Driver i
>> ffffffffc059279c: 646f6d207325206e 6974736554000a65 n %s mode..Testi
>> ffffffffc05927ac: 636976656420676e 786c252074612065 ng device at %lx
>> ffffffffc05927bc: 6b63656843000a2e 646f727020676e69 ...Checking prod
>> ffffffffc05927cc: 6f20444920746375 0a2e706968632066 uct ID of chip..
>> ffffffffc05927dc: 5120646e756f4600 204130303232414c .Found QLA2200A
>> ffffffffc05927ec: 43000a2e70696843 20676e696b636568 Chip...Checking
>> ffffffffc05927fc: 65786f626c69616d 6c636e69000a2e73 mailboxes...incl
>> ffffffffc059280c: 756e696c2f656475 616d2d616d642f78 ude/linux/dma-ma
>>
>> crash> struct -ox srb_iocb
>> struct srb_iocb {
>> union {
>> struct {...} logio;
>> struct {...} els_logo;
>> struct {...} tmf;
>> struct {...} fxiocb;
>> struct {...} abt;
>> struct ct_arg ctarg;
>> struct {...} mbx;
>> struct {...} nack;
>> [0x0 ] } u;
>> [0xb8] struct timer_list timer;
>> [0x108] void (*timeout)(void *);
>> }
>> SIZE: 0x110
>>
>> crash> ! bc
>> ibase=16
>> obase=10
>> B8+40
>> F8
>>
>> The object is a srb_t, and at offset 0xf8 within that structure
>> (i.e. ffff95e5ff621080 + f8 -> ffff95e5ff621178) is a struct timer_list.
>>
>> Cc: <stable@xxxxxxxxxxxxxxx> #4.4+
>> Signed-off-by: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
>> ---
>> Hi Martin,
>>
>> This patch addresses crash due to NULL pointer access because driver
>> left active timer running for abort IOCB.
>>
>> Please apply this patch to 4.16/scsi-fixes at your earliest convenience.
>>
>> Thanks,
>> Himanshu
>> ---
>> drivers/scsi/qla2xxx/qla_init.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/scsi/qla2xxx/qla_init.c b/drivers/scsi/qla2xxx/qla_init.c
>> index 2dea1129d396..04870621e712 100644
>> --- a/drivers/scsi/qla2xxx/qla_init.c
>> +++ b/drivers/scsi/qla2xxx/qla_init.c
>> @@ -1527,6 +1527,7 @@ `(void *ptr, int res)
>> srb_t *sp = ptr;
>> struct srb_iocb *abt = &sp->u.iocb_cmd;
>>
>> + del_timer(&sp->u.iocb_cmd.timer);
>
> Hi,
>
> I am not familiar with this code. But I note that this abort seems to be "asynchronous" (I see it's setup in qla24xx_async_abort_cmd()), so do you need the "sync" variant of del_timer() for safety? This would be to ensure the timeout has not actually occurred and is racing with the "done" callback?
>
after reviewing code for the usage of timer i see that qla24xx_async_abort_cmd() would not be adding timer back even though the call is
asynchronous. I think its safe to use only del_timer().
> Thanks,
> John
>
>> complete(&abt->u.abt.comp);
>> }
Thanks,
- Himanshu
