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


On Tuesday 25 February 2020 04:41:48 Bart Van Assche wrote:
> 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.

Thank you very much for the analysis.
Unfortunately, QLogic does not seem to care...

--
Ondrej Zary

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