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Subject[PATCH 4.20 070/183] acpi/nfit: Fix race accessing memdev in nfit_get_smbios_id()
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 0919871ac37fdcf46c7657da0f1742efe096b399 ]

Possible race accessing memdev structures after dropping the
mutex. Dan Williams says this could race against another thread
that is doing:

# echo "ACPI0012:00" > /sys/bus/acpi/drivers/nfit/unbind

Reported-by: Jane Chu <jane.chu@oracle.com>
Fixes: 23222f8f8dce ("acpi, nfit: Add function to look up nvdimm...")
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/nfit/core.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index 8535e7999769b..2a2d7ec772526 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -724,6 +724,7 @@ int nfit_get_smbios_id(u32 device_handle, u16 *flags)
struct acpi_nfit_memory_map *memdev;
struct acpi_nfit_desc *acpi_desc;
struct nfit_mem *nfit_mem;
+ u16 physical_id;

mutex_lock(&acpi_desc_lock);
list_for_each_entry(acpi_desc, &acpi_descs, list) {
@@ -731,10 +732,11 @@ int nfit_get_smbios_id(u32 device_handle, u16 *flags)
list_for_each_entry(nfit_mem, &acpi_desc->dimms, list) {
memdev = __to_nfit_memdev(nfit_mem);
if (memdev->device_handle == device_handle) {
+ *flags = memdev->flags;
+ physical_id = memdev->physical_id;
mutex_unlock(&acpi_desc->init_mutex);
mutex_unlock(&acpi_desc_lock);
- *flags = memdev->flags;
- return memdev->physical_id;
+ return physical_id;
}
}
mutex_unlock(&acpi_desc->init_mutex);
--
2.19.1


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