Re: [PATCH] pmem: fix the crash when unbind namespaces

[Dan Williams]

On Sun, Aug 22, 2021 at 4:49 AM <sumiyawang@xxxxxxxxx> wrote:
>
> From: sumiyawang <sumiyawang@xxxxxxxxxxx>
>
> kernel will crash when use after free the ioremap space,
> which is triggered by ndctl destroy-namespace while some IO operations
> exist.
> The sequence of pmem driver release chain should be changed:
> freeze the queue and wait io finished first, then iounmap.
>
> [47202.018374] BUG: unable to handle page fault for address: ffffc90080200000
> [47202.018822] CPU: 36 PID: 9606 Comm: systemd-udevd
> [47202.020921] Call Trace:
> [47202.020969]  ? pmem_do_bvec+0xf9/0x3a0
> [47202.021036]  ? xas_alloc+0x55/0xd0
> [47202.021094]  pmem_rw_page+0x4b/0x80
> [47202.021159]  bdev_read_page+0x86/0xb0
> [47202.021222]  do_mpage_readpage+0x5d4/0x7a0
> [47202.021297]  ? lru_cache_add+0xe/0x10
> [47202.021359]  mpage_readpages+0xf9/0x1c0
> [47202.021428]  ? bd_link_disk_holder+0x1a0/0x1a0
> [47202.021506]  blkdev_readpages+0x1d/0x20
> [47202.021574]  read_pages+0x67/0x1a0
>
> ndctl Call Trace in vmcore:
> PID: 23473  TASK: ffff88c4fbbe8000  CPU: 1   COMMAND: "ndctl"
> __schedule
> schedule
> blk_mq_freeze_queue_wait
> blk_freeze_queue
> blk_cleanup_queue
> pmem_release_queue
> devm_action_release
> release_nodes
> devres_release_all
> device_release_driver_internal
> device_driver_detach
> unbind_store
>
> At that time, the ioremap space is released

Thanks, looks good. I reworded the changelog a bit and added a "Cc:
stable" as well as a "Fixes: 50f44ee7248a ("mm/devm_memremap_pages:
fix final page put race")" tag. I'll send this up during the v5.15
merge window.

https://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm.git/commit/?h=libnvdimm-fixes&id=32b2397c