Re: NULL pointer dereference in qla24xx_abort_command, kernel 4.19.98 (Debian)

Bart Van Assche
2020-02-25T03:41:54Z

On 2020-02-24 00:20, Ondrej Zary wrote:
> Looks like it's in some inlined function.
>
> /usr/src/linux-source-4.19# gdb /lib/modules/4.19.0-8-amd64/kernel/drivers/scsi/qla2xxx/qla2xxx.ko
> GNU gdb (Debian 8.2.1-2+b3) 8.2.1
> ...
> Reading symbols from /lib/modules/4.19.0-8-amd64/kernel/drivers/scsi/qla2xxx/qla2xxx.ko...Reading symbols
> from /usr/lib/debug//lib/modules/4.19.0-8-amd64/kernel/drivers/scsi/qla2xxx/qla2xxx.ko...done.
> done.
>
> (gdb) list *(qla24xx_async_abort_cmd+0x1b)
> 0xf88b is in qla24xx_async_abort_cmd (./arch/x86/include/asm/atomic.h:97).
> 92 *
> 93 * Atomically increments @v by 1.
> 94 */
> 95 static __always_inline void arch_atomic_inc(atomic_t *v)
> 96 {
> 97 asm volatile(LOCK_PREFIX "incl %0"
> 98 : "+m" (v->counter) :: "memory");
> 99 }
> 100 #define arch_atomic_inc arch_atomic_inc
>
> [ ... ]
>
> (gdb) disassemble qla24xx_async_abort_cmd
> Dump of assembler code for function qla24xx_async_abort_cmd:
> 0x000000000000f870 <+0>: callq 0xf875 <qla24xx_async_abort_cmd+5>
> 0x000000000000f875 <+5>: push %r15
> 0x000000000000f877 <+7>: push %r14
> 0x000000000000f879 <+9>: push %r13
> 0x000000000000f87b <+11>: push %r12
> 0x000000000000f87d <+13>: push %rbp
> 0x000000000000f87e <+14>: push %rbx
> 0x000000000000f87f <+15>: mov 0x28(%rdi),%r13
> 0x000000000000f883 <+19>: mov 0x20(%rdi),%r15
> 0x000000000000f887 <+23>: mov 0x48(%rdi),%r14
> 0x000000000000f88b <+27>: lock incl 0x4(%r14)
> 0x000000000000f890 <+32>: mfence

Thanks, this is very helpful. I think the above means that the crash is
triggered by the following code:

sp = qla2xxx_get_qpair_sp(cmd_sp->qpair, cmd_sp->fcport,
GFP_KERNEL);

From the start of qla2xxx_get_qpair_sp():

QLA_QPAIR_MARK_BUSY(qpair, bail);

From qla_def.h:

#define QLA_QPAIR_MARK_BUSY(__qpair, __bail) do { \
atomic_inc(&__qpair->ref_count); \
mb(); \
if (__qpair->delete_in_progress) { \
atomic_dec(&__qpair->ref_count); \
__bail = 1; \
} else { \
__bail = 0; \
} \
} while (0)

One of the changes between kernel version v4.9.210 and v4.19.98 is the
following: "qla2xxx: Add multiple queue pair functionality". I think the
above information means that the cmd_sp->qpair pointer is NULL. I will
let QLogic recommend a solution.

Bart.