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SubjectRe: [PATCH] drivers/scsi/qla2xxx: fix double free bug after firmware timeout
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Hi Max,

> On Dec 7, 2017, at 6:46 AM, Max Kellermann <mk@cm4all.com> wrote:
>
> When the qla2xxx firmware is unavailable, eventually
> qla2x00_sp_timeout() is reached, which calls the timeout function and
> frees the srb_t instance.
>
> The timeout function always resolves to qla2x00_async_iocb_timeout(),
> which invokes another callback function called "done". All of these
> qla2x00_*_sp_done() callbacks also free the srb_t instance; after
> returning to qla2x00_sp_timeout(), it is freed again.
>
> The fix is to remove the "sp->free(sp)" call from qla2x00_sp_timeout()
> and add it to those code paths in qla2x00_async_iocb_timeout() which
> do not already free the object.
>
> This is how it looks like with KASAN:
>
> BUG: KASAN: use-after-free in qla2x00_sp_timeout+0x228/0x250
> Read of size 8 at addr ffff88278147a590 by task swapper/2/0
>
> Allocated by task 1502:
> save_stack+0x33/0xa0
> kasan_kmalloc+0xa0/0xd0
> kmem_cache_alloc+0xb8/0x1c0
> mempool_alloc+0xd6/0x260
> qla24xx_async_gnl+0x3c5/0x1100
>
> Freed by task 0:
> save_stack+0x33/0xa0
> kasan_slab_free+0x72/0xc0
> kmem_cache_free+0x75/0x200
> qla24xx_async_gnl_sp_done+0x556/0x9e0
> qla2x00_async_iocb_timeout+0x1c7/0x420
> qla2x00_sp_timeout+0x16d/0x250
> call_timer_fn+0x36/0x200
>
> The buggy address belongs to the object at ffff88278147a440
> which belongs to the cache qla2xxx_srbs of size 344
> The buggy address is located 336 bytes inside of
> 344-byte region [ffff88278147a440, ffff88278147a598)
>
> Signed-off-by: Max Kellermann <mk@cm4all.com>
> ---
> drivers/scsi/qla2xxx/qla_init.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/qla2xxx/qla_init.c b/drivers/scsi/qla2xxx/qla_init.c
> index b5b48ddca962..801890564e00 100644
> --- a/drivers/scsi/qla2xxx/qla_init.c
> +++ b/drivers/scsi/qla2xxx/qla_init.c
> @@ -58,7 +58,6 @@ qla2x00_sp_timeout(unsigned long __data)
> req->outstanding_cmds[sp->handle] = NULL;
> iocb = &sp->u.iocb_cmd;
> iocb->timeout(sp);
> - sp->free(sp);
> spin_unlock_irqrestore(&vha->hw->hardware_lock, flags);
> }
>
> @@ -121,9 +120,11 @@ qla2x00_async_iocb_timeout(void *data)
> ea.data[1] = lio->u.logio.data[1];
> ea.sp = sp;
> qla24xx_handle_plogi_done_event(fcport->vha, &ea);
> + sp->free(sp);
> break;
> case SRB_LOGOUT_CMD:
> qlt_logo_completion_handler(fcport, QLA_FUNCTION_TIMEOUT);
> + sp->free(sp);
> break;
> case SRB_CT_PTHRU_CMD:
> case SRB_MB_IOCB:
>


NACK

These calls are asynchronous calls and free should be called by completion.

I am going to send updates to driver which we have fixed similar issue for 4.16

Thanks,
- Himanshu

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