Hi Max, > On Jan 15, 2018, at 9:26 AM, Max Kellermann <mk@xxxxxxxxxx> 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@xxxxxxxxxx> > --- > 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: > We have patch to prevent this double free in 4.16/scsi-queue already. https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git/commit/?h=4.16/scsi-queue&id=045d6ea200af794ba15515984cff63787a7fc3c0 Thanks, - Himanshu
