This is a note to let you know that I've just added the patch titled
cxl/pmem: Fix nvdimm registration races
to the 6.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
cxl-pmem-fix-nvdimm-registration-races.patch
and it can be found in the queue-6.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f57aec443c24d2e8e1f3b5b4856aea12ddda4254 Mon Sep 17 00:00:00 2001
From: Dan Williams <dan.j.williams@xxxxxxxxx>
Date: Mon, 13 Feb 2023 17:01:05 -0800
Subject: cxl/pmem: Fix nvdimm registration races
From: Dan Williams <dan.j.williams@xxxxxxxxx>
commit f57aec443c24d2e8e1f3b5b4856aea12ddda4254 upstream.
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@xxxxxxxxxxxxxxx>
Reported-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/cxl/pmem.c | 1 +
drivers/nvdimm/bus.c | 19 ++++++++++++++++---
drivers/nvdimm/dimm_devs.c | 5 ++++-
drivers/nvdimm/nd-core.h | 1 +
include/linux/libnvdimm.h | 3 +++
5 files changed, 25 insertions(+), 4 deletions(-)
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -76,6 +76,7 @@ static int cxl_nvdimm_probe(struct devic
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);
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -508,7 +508,7 @@ static void nd_async_device_unregister(v
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 *d
}
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;
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -624,7 +624,10 @@ struct nvdimm *__nvdimm_create(struct nv
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;
}
--- a/drivers/nvdimm/nd-core.h
+++ b/drivers/nvdimm/nd-core.h
@@ -107,6 +107,7 @@ int nvdimm_bus_create_ndctl(struct nvdim
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);
--- 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,
Patches currently in stable-queue which might be from dan.j.williams@xxxxxxxxx are
queue-6.2/dax-kmem-fix-leak-of-memory-hotplug-resources.patch
queue-6.2/cxl-pmem-fix-nvdimm-registration-races.patch
