The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f57aec443c24d2e8e1f3b5b4856aea12ddda4254 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '1678181685158238@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

f57aec443c24 ("cxl/pmem: Fix nvdimm registration races") 4a0079bc7aae ("nvdimm: Replace lockdep_mutex with local lock classes") 3b6c6c039707 ("nvdimm/region: Delete nd_blk_region infrastructure") 84bd3690bf54 ("nvdimm/namespace: Delete nd_namespace_blk") fadc38a6672a ("nvdimm/namespace: Delete blk namespace consideration in shared paths") d9d290d7e659 ("nvdimm/region: Fix default alignment for small regions") 60b8f17215de ("cxl/pmem: Translate NVDIMM label commands to CXL label commands") 12f3856ad42d ("cxl/mbox: Add exclusive kernel command support") ff56ab9e164d ("cxl/mbox: Convert 'enabled_cmds' to DECLARE_BITMAP") 4faf31b43468 ("cxl/mbox: Move mailbox and other non-PCI specific infrastructure to the core") 4cb35f1ca05a ("cxl/pci: Drop idr.h") b64955a92929 ("cxl/mbox: Introduce the mbox_send operation") 13e7749d06b3 ("cxl/pci: Clean up cxl_mem_get_partition_info()") 99e222a5f1b6 ("cxl/pci: Make 'struct cxl_mem' device type generic") 5af96835e4da ("libnvdimm/labels: Introduce CXL labels") 540ccaa2e4dd ("libnvdimm/label: Define CXL region labels") 42e192aa9891 ("libnvdimm/labels: Introduce the concept of multi-range namespace labels") 8172db92527c ("libnvdimm/label: Add a helper for nlabel validation") d1c6e08e7503 ("libnvdimm/labels: Add uuid helpers")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f57aec443c24d2e8e1f3b5b4856aea12ddda4254 Mon Sep 17 00:00:00 2001 From: Dan Williams dan.j.williams@intel.com Date: Mon, 13 Feb 2023 17:01:05 -0800 Subject: [PATCH] cxl/pmem: Fix nvdimm registration races

A loop of the form:

while true; do modprobe cxl_pci; modprobe -r cxl_pci; done

...fails with the following crash signature:

BUG: kernel NULL pointer dereference, address: 0000000000000040 [..] RIP: 0010:cxl_internal_send_cmd+0x5/0xb0 [cxl_core] [..] Call Trace: <TASK> cxl_pmem_ctl+0x121/0x240 [cxl_pmem] nvdimm_get_config_data+0xd6/0x1a0 [libnvdimm] nd_label_data_init+0x135/0x7e0 [libnvdimm] nvdimm_probe+0xd6/0x1c0 [libnvdimm] nvdimm_bus_probe+0x7a/0x1e0 [libnvdimm] really_probe+0xde/0x380 __driver_probe_device+0x78/0x170 driver_probe_device+0x1f/0x90 __device_attach_driver+0x85/0x110 bus_for_each_drv+0x7d/0xc0 __device_attach+0xb4/0x1e0 bus_probe_device+0x9f/0xc0 device_add+0x445/0x9c0 nd_async_device_register+0xe/0x40 [libnvdimm] async_run_entry_fn+0x30/0x130

...namely that the bottom half of async nvdimm device registration runs after the CXL has already torn down the context that cxl_pmem_ctl() needs. Unlike the ACPI NFIT case that benefits from launching multiple nvdimm device registrations in parallel from those listed in the table, CXL is already marked PROBE_PREFER_ASYNCHRONOUS. So provide for a synchronous registration path to preclude this scenario.

Fixes: 21083f51521f ("cxl/pmem: Register 'pmem' / cxl_nvdimm devices") Cc: stable@vger.kernel.org Reported-by: Dave Jiang dave.jiang@intel.com Signed-off-by: Dan Williams dan.j.williams@intel.com

diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c index 08bbbac9a6d0..71cfa1fdf902 100644 --- a/drivers/cxl/pmem.c +++ b/drivers/cxl/pmem.c @@ -76,6 +76,7 @@ static int cxl_nvdimm_probe(struct device *dev) return rc;

set_bit(NDD_LABELING, &flags); + set_bit(NDD_REGISTER_SYNC, &flags); set_bit(ND_CMD_GET_CONFIG_SIZE, &cmd_mask); set_bit(ND_CMD_GET_CONFIG_DATA, &cmd_mask); set_bit(ND_CMD_SET_CONFIG_DATA, &cmd_mask); diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c index b38d0355b0ac..5ad49056921b 100644 --- a/drivers/nvdimm/bus.c +++ b/drivers/nvdimm/bus.c @@ -508,7 +508,7 @@ static void nd_async_device_unregister(void *d, async_cookie_t cookie) put_device(dev); }

-void nd_device_register(struct device *dev) +static void __nd_device_register(struct device *dev, bool sync) { if (!dev) return; @@ -531,11 +531,24 @@ void nd_device_register(struct device *dev) } get_device(dev);

- async_schedule_dev_domain(nd_async_device_register, dev, - &nd_async_domain); + if (sync) + nd_async_device_register(dev, 0); + else + async_schedule_dev_domain(nd_async_device_register, dev, + &nd_async_domain); +} + +void nd_device_register(struct device *dev) +{ + __nd_device_register(dev, false); } EXPORT_SYMBOL(nd_device_register);

+void nd_device_register_sync(struct device *dev) +{ + __nd_device_register(dev, true); +} + void nd_device_unregister(struct device *dev, enum nd_async_mode mode) { bool killed; diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c index 1fc081dcf631..6d3b03a9fa02 100644 --- a/drivers/nvdimm/dimm_devs.c +++ b/drivers/nvdimm/dimm_devs.c @@ -624,7 +624,10 @@ struct nvdimm *__nvdimm_create(struct nvdimm_bus *nvdimm_bus, nvdimm->sec.ext_flags = nvdimm_security_flags(nvdimm, NVDIMM_MASTER); device_initialize(dev); lockdep_set_class(&dev->mutex, &nvdimm_key); - nd_device_register(dev); + if (test_bit(NDD_REGISTER_SYNC, &flags)) + nd_device_register_sync(dev); + else + nd_device_register(dev);

return nvdimm; } diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h index cc86ee09d7c0..845408f10655 100644 --- a/drivers/nvdimm/nd-core.h +++ b/drivers/nvdimm/nd-core.h @@ -107,6 +107,7 @@ int nvdimm_bus_create_ndctl(struct nvdimm_bus *nvdimm_bus); void nvdimm_bus_destroy_ndctl(struct nvdimm_bus *nvdimm_bus); void nd_synchronize(void); void nd_device_register(struct device *dev); +void nd_device_register_sync(struct device *dev); struct nd_label_id; char *nd_label_gen_id(struct nd_label_id *label_id, const uuid_t *uuid, u32 flags); diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h index af38252ad704..e772aae71843 100644 --- a/include/linux/libnvdimm.h +++ b/include/linux/libnvdimm.h @@ -41,6 +41,9 @@ enum { */ NDD_INCOHERENT = 7,

+ /* dimm provider wants synchronous registration by __nvdimm_create() */ + NDD_REGISTER_SYNC = 8, + /* need to set a limit somewhere, but yes, this is likely overkill */ ND_IOCTL_MAX_BUFLEN = SZ_4M, ND_CMD_MAX_ELEM = 5,