[PATCH AUTOSEL 4.14 1/8] NFSv4: nfs4_proc_set_acl needs to restore NFS_CAP_UIDGID_NOMAP on error.

[PATCH AUTOSEL 4.14 1/8] NFSv4: nfs4_proc_set_acl needs to restore NFS_CAP_UIDGID_NOMAP on error.

[Sasha Levin]

From: Dai Ngo <dai.ngo@oracle.com>

[ Upstream commit f8849e206ef52b584cd9227255f4724f0cc900bb ]

Currently if __nfs4_proc_set_acl fails with NFS4ERR_BADOWNER it
re-enables the idmapper by clearing NFS_CAP_UIDGID_NOMAP before
retrying again. The NFS_CAP_UIDGID_NOMAP remains cleared even if
the retry fails. This causes problem for subsequent setattr
requests for v4 server that does not have idmapping configured.

This patch modifies nfs4_proc_set_acl to detect NFS4ERR_BADOWNER
and NFS4ERR_BADNAME and skips the retry, since the kernel isn't
involved in encoding the ACEs, and return -EINVAL.

Steps to reproduce the problem:

 # mount -o vers=4.1,sec=sys server:/export/test /tmp/mnt
 # touch /tmp/mnt/file1
 # chown 99 /tmp/mnt/file1
 # nfs4_setfacl -a A::unknown.user@xyz.com:wrtncy /tmp/mnt/file1
 Failed setxattr operation: Invalid argument
 # chown 99 /tmp/mnt/file1
 chown: changing ownership of ‘/tmp/mnt/file1’: Invalid argument
 # umount /tmp/mnt
 # mount -o vers=4.1,sec=sys server:/export/test /tmp/mnt
 # chown 99 /tmp/mnt/file1
 #

v2: detect NFS4ERR_BADOWNER and NFS4ERR_BADNAME and skip retry
       in nfs4_proc_set_acl.
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfs/nfs4proc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index e053fd7f83d8..ae19ead908d5 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5294,6 +5294,14 @@ static int nfs4_proc_set_acl(struct inode *inode, const void *buf, size_t buflen
 	do {
 		err = __nfs4_proc_set_acl(inode, buf, buflen);
 		trace_nfs4_set_acl(inode, err);
+		if (err == -NFS4ERR_BADOWNER || err == -NFS4ERR_BADNAME) {
+			/*
+			 * no need to retry since the kernel
+			 * isn't involved in encoding the ACEs.
+			 */
+			err = -EINVAL;
+			break;
+		}
 		err = nfs4_handle_exception(NFS_SERVER(inode), err,
 				&exception);
 	} while (exception.retry);
-- 
2.30.2

[PATCH AUTOSEL 4.14 2/8] scsi: core: Fix error handling of scsi_host_alloc()

[Sasha Levin]

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 66a834d092930cf41d809c0e989b13cd6f9ca006 ]

After device is initialized via device_initialize(), or its name is set via
dev_set_name(), the device has to be freed via put_device().  Otherwise
device name will be leaked because it is allocated dynamically in
dev_set_name().

Fix the leak by replacing kfree() with put_device(). Since
scsi_host_dev_release() properly handles IDA and kthread removal, remove
special-casing these from the error handling as well.

Link: https://lore.kernel.org/r/20210602133029.2864069-2-ming.lei@redhat.com
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/hosts.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index ef22b275d050..7f99f02aef1c 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -404,8 +404,10 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	mutex_init(&shost->scan_mutex);
 
 	index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
-	if (index < 0)
-		goto fail_kfree;
+	if (index < 0) {
+		kfree(shost);
+		return NULL;
+	}
 	shost->host_no = index;
 
 	shost->dma_channel = 0xff;
@@ -493,7 +495,7 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 		shost_printk(KERN_WARNING, shost,
 			"error handler thread failed to spawn, error = %ld\n",
 			PTR_ERR(shost->ehandler));
-		goto fail_index_remove;
+		goto fail;
 	}
 
 	shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
@@ -502,17 +504,18 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 	if (!shost->tmf_work_q) {
 		shost_printk(KERN_WARNING, shost,
 			     "failed to create tmf workq\n");
-		goto fail_kthread;
+		goto fail;
 	}
 	scsi_proc_hostdir_add(shost->hostt);
 	return shost;
+ fail:
+	/*
+	 * Host state is still SHOST_CREATED and that is enough to release
+	 * ->shost_gendev. scsi_host_dev_release() will free
+	 * dev_name(&shost->shost_dev).
+	 */
+	put_device(&shost->shost_gendev);
 
- fail_kthread:
-	kthread_stop(shost->ehandler);
- fail_index_remove:
-	ida_simple_remove(&host_index_ida, shost->host_no);
- fail_kfree:
-	kfree(shost);
 	return NULL;
 }
 EXPORT_SYMBOL(scsi_host_alloc);
-- 
2.30.2

[PATCH AUTOSEL 4.14 3/8] scsi: core: Put .shost_dev in failure path if host state changes to RUNNING

[Sasha Levin]

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 11714026c02d613c30a149c3f4c4a15047744529 ]

scsi_host_dev_release() only frees dev_name when host state is
SHOST_CREATED. After host state has changed to SHOST_RUNNING,
scsi_host_dev_release() no longer cleans up.

Fix this by doing a put_device(&shost->shost_dev) in the failure path when
host state is SHOST_RUNNING. Move get_device(&shost->shost_gendev) before
device_add(&shost->shost_dev) so that scsi_host_cls_release() can do a put
on this reference.

Link: https://lore.kernel.org/r/20210602133029.2864069-4-ming.lei@redhat.com
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.de>
Reported-by: John Garry <john.garry@huawei.com>
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/hosts.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 7f99f02aef1c..ff92df3fe401 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -256,12 +256,11 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
 
 	device_enable_async_suspend(&shost->shost_dev);
 
+	get_device(&shost->shost_gendev);
 	error = device_add(&shost->shost_dev);
 	if (error)
 		goto out_del_gendev;
 
-	get_device(&shost->shost_gendev);
-
 	if (shost->transportt->host_size) {
 		shost->shost_data = kzalloc(shost->transportt->host_size,
 					 GFP_KERNEL);
@@ -298,6 +297,11 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
  out_del_dev:
 	device_del(&shost->shost_dev);
  out_del_gendev:
+	/*
+	 * Host state is SHOST_RUNNING so we have to explicitly release
+	 * ->shost_dev.
+	 */
+	put_device(&shost->shost_dev);
 	device_del(&shost->shost_gendev);
  out_disable_runtime_pm:
 	device_disable_async_suspend(&shost->shost_gendev);
-- 
2.30.2

[PATCH AUTOSEL 4.14 4/8] scsi: core: Only put parent device if host state differs from SHOST_CREATED

[Sasha Levin]

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 1e0d4e6225996f05271de1ebcb1a7c9381af0b27 ]

get_device(shost->shost_gendev.parent) is called after host state has
switched to SHOST_RUNNING. scsi_host_dev_release() shouldn't release the
parent device if host state is still SHOST_CREATED.

Link: https://lore.kernel.org/r/20210602133029.2864069-5-ming.lei@redhat.com
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: John Garry <john.garry@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/hosts.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index ff92df3fe401..5788a2ce3571 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -355,7 +355,7 @@ static void scsi_host_dev_release(struct device *dev)
 
 	ida_simple_remove(&host_index_ida, shost->host_no);
 
-	if (parent)
+	if (shost->shost_state != SHOST_CREATED)
 		put_device(parent);
 	kfree(shost);
 }
-- 
2.30.2

[PATCH AUTOSEL 4.14 5/8] radeon: use memcpy_to/fromio for UVD fw upload

[Sasha Levin]

From: Chen Li <chenli@uniontech.com>

[ Upstream commit ab8363d3875a83f4901eb1cc00ce8afd24de6c85 ]

I met a gpu addr bug recently and the kernel log
tells me the pc is memcpy/memset and link register is
radeon_uvd_resume.

As we know, in some architectures, optimized memcpy/memset
may not work well on device memory. Trival memcpy_toio/memset_io
can fix this problem.

BTW, amdgpu has already done it in:
commit ba0b2275a678 ("drm/amdgpu: use memcpy_to/fromio for UVD fw upload"),
that's why it has no this issue on the same gpu and platform.

Signed-off-by: Chen Li <chenli@uniontech.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/radeon/radeon_uvd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_uvd.c b/drivers/gpu/drm/radeon/radeon_uvd.c
index 95f4db70dd22..fde9c69ecc86 100644
--- a/drivers/gpu/drm/radeon/radeon_uvd.c
+++ b/drivers/gpu/drm/radeon/radeon_uvd.c
@@ -286,7 +286,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	if (rdev->uvd.vcpu_bo == NULL)
 		return -EINVAL;
 
-	memcpy(rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
+	memcpy_toio((void __iomem *)rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
 
 	size = radeon_bo_size(rdev->uvd.vcpu_bo);
 	size -= rdev->uvd_fw->size;
@@ -294,7 +294,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	ptr = rdev->uvd.cpu_addr;
 	ptr += rdev->uvd_fw->size;
 
-	memset(ptr, 0, size);
+	memset_io((void __iomem *)ptr, 0, size);
 
 	return 0;
 }
-- 
2.30.2

[PATCH AUTOSEL 4.14 5/8] radeon: use memcpy_to/fromio for UVD fw upload

[Sasha Levin]

From: Chen Li <chenli@uniontech.com>

[ Upstream commit ab8363d3875a83f4901eb1cc00ce8afd24de6c85 ]

I met a gpu addr bug recently and the kernel log
tells me the pc is memcpy/memset and link register is
radeon_uvd_resume.

As we know, in some architectures, optimized memcpy/memset
may not work well on device memory. Trival memcpy_toio/memset_io
can fix this problem.

BTW, amdgpu has already done it in:
commit ba0b2275a678 ("drm/amdgpu: use memcpy_to/fromio for UVD fw upload"),
that's why it has no this issue on the same gpu and platform.

Signed-off-by: Chen Li <chenli@uniontech.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/radeon/radeon_uvd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_uvd.c b/drivers/gpu/drm/radeon/radeon_uvd.c
index 95f4db70dd22..fde9c69ecc86 100644
--- a/drivers/gpu/drm/radeon/radeon_uvd.c
+++ b/drivers/gpu/drm/radeon/radeon_uvd.c
@@ -286,7 +286,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	if (rdev->uvd.vcpu_bo == NULL)
 		return -EINVAL;
 
-	memcpy(rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
+	memcpy_toio((void __iomem *)rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
 
 	size = radeon_bo_size(rdev->uvd.vcpu_bo);
 	size -= rdev->uvd_fw->size;
@@ -294,7 +294,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	ptr = rdev->uvd.cpu_addr;
 	ptr += rdev->uvd_fw->size;
 
-	memset(ptr, 0, size);
+	memset_io((void __iomem *)ptr, 0, size);
 
 	return 0;
 }
-- 
2.30.2

_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

[PATCH AUTOSEL 4.14 5/8] radeon: use memcpy_to/fromio for UVD fw upload

[Sasha Levin]

From: Chen Li <chenli@uniontech.com>

[ Upstream commit ab8363d3875a83f4901eb1cc00ce8afd24de6c85 ]

I met a gpu addr bug recently and the kernel log
tells me the pc is memcpy/memset and link register is
radeon_uvd_resume.

As we know, in some architectures, optimized memcpy/memset
may not work well on device memory. Trival memcpy_toio/memset_io
can fix this problem.

BTW, amdgpu has already done it in:
commit ba0b2275a678 ("drm/amdgpu: use memcpy_to/fromio for UVD fw upload"),
that's why it has no this issue on the same gpu and platform.

Signed-off-by: Chen Li <chenli@uniontech.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/radeon/radeon_uvd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_uvd.c b/drivers/gpu/drm/radeon/radeon_uvd.c
index 95f4db70dd22..fde9c69ecc86 100644
--- a/drivers/gpu/drm/radeon/radeon_uvd.c
+++ b/drivers/gpu/drm/radeon/radeon_uvd.c
@@ -286,7 +286,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	if (rdev->uvd.vcpu_bo == NULL)
 		return -EINVAL;
 
-	memcpy(rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
+	memcpy_toio((void __iomem *)rdev->uvd.cpu_addr, rdev->uvd_fw->data, rdev->uvd_fw->size);
 
 	size = radeon_bo_size(rdev->uvd.vcpu_bo);
 	size -= rdev->uvd_fw->size;
@@ -294,7 +294,7 @@ int radeon_uvd_resume(struct radeon_device *rdev)
 	ptr = rdev->uvd.cpu_addr;
 	ptr += rdev->uvd_fw->size;
 
-	memset(ptr, 0, size);
+	memset_io((void __iomem *)ptr, 0, size);
 
 	return 0;
 }
-- 
2.30.2

[PATCH AUTOSEL 4.14 6/8] kvm: avoid speculation-based attacks from out-of-range memslot accesses

[Sasha Levin]

From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit da27a83fd6cc7780fea190e1f5c19e87019da65c ]

KVM's mechanism for accessing guest memory translates a guest physical
address (gpa) to a host virtual address using the right-shifted gpa
(also known as gfn) and a struct kvm_memory_slot.  The translation is
performed in __gfn_to_hva_memslot using the following formula:

      hva = slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE

It is expected that gfn falls within the boundaries of the guest's
physical memory.  However, a guest can access invalid physical addresses
in such a way that the gfn is invalid.

__gfn_to_hva_memslot is called from kvm_vcpu_gfn_to_hva_prot, which first
retrieves a memslot through __gfn_to_memslot.  While __gfn_to_memslot
does check that the gfn falls within the boundaries of the guest's
physical memory or not, a CPU can speculate the result of the check and
continue execution speculatively using an illegal gfn. The speculation
can result in calculating an out-of-bounds hva.  If the resulting host
virtual address is used to load another guest physical address, this
is effectively a Spectre gadget consisting of two consecutive reads,
the second of which is data dependent on the first.

Right now it's not clear if there are any cases in which this is
exploitable.  One interesting case was reported by the original author
of this patch, and involves visiting guest page tables on x86.  Right
now these are not vulnerable because the hva read goes through get_user(),
which contains an LFENCE speculation barrier.  However, there are
patches in progress for x86 uaccess.h to mask kernel addresses instead of
using LFENCE; once these land, a guest could use speculation to read
from the VMM's ring 3 address space.  Other architectures such as ARM
already use the address masking method, and would be susceptible to
this same kind of data-dependent access gadgets.  Therefore, this patch
proactively protects from these attacks by masking out-of-bounds gfns
in __gfn_to_hva_memslot, which blocks speculation of invalid hvas.

Sean Christopherson noted that this patch does not cover
kvm_read_guest_offset_cached.  This however is limited to a few bytes
past the end of the cache, and therefore it is unlikely to be useful in
the context of building a chain of data dependent accesses.

Reported-by: Artemiy Margaritov <artemiy.margaritov@gmail.com>
Co-developed-by: Artemiy Margaritov <artemiy.margaritov@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/kvm_host.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2e06ca46f07c..a28a5c80f117 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -963,7 +963,15 @@ __gfn_to_memslot(struct kvm_memslots *slots, gfn_t gfn)
 static inline unsigned long
 __gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
 {
-	return slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE;
+	/*
+	 * The index was checked originally in search_memslots.  To avoid
+	 * that a malicious guest builds a Spectre gadget out of e.g. page
+	 * table walks, do not let the processor speculate loads outside
+	 * the guest's registered memslots.
+	 */
+	unsigned long offset = array_index_nospec(gfn - slot->base_gfn,
+						  slot->npages);
+	return slot->userspace_addr + offset * PAGE_SIZE;
 }
 
 static inline int memslot_id(struct kvm *kvm, gfn_t gfn)
-- 
2.30.2

[PATCH AUTOSEL 4.14 7/8] kvm: fix previous commit for 32-bit builds

[Sasha Levin]

From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit 4422829e8053068e0225e4d0ef42dc41ea7c9ef5 ]

array_index_nospec does not work for uint64_t on 32-bit builds.
However, the size of a memory slot must be less than 20 bits wide
on those system, since the memory slot must fit in the user
address space.  So just store it in an unsigned long.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/kvm_host.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a28a5c80f117..d5e38ebcfa47 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -969,8 +969,8 @@ __gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
 	 * table walks, do not let the processor speculate loads outside
 	 * the guest's registered memslots.
 	 */
-	unsigned long offset = array_index_nospec(gfn - slot->base_gfn,
-						  slot->npages);
+	unsigned long offset = gfn - slot->base_gfn;
+	offset = array_index_nospec(offset, slot->npages);
 	return slot->userspace_addr + offset * PAGE_SIZE;
 }
 
-- 
2.30.2

[PATCH AUTOSEL 4.14 8/8] hwmon: (scpi-hwmon) shows the negative temperature properly

[Sasha Levin]

From: Riwen Lu <luriwen@kylinos.cn>

[ Upstream commit 78d13552346289bad4a9bf8eabb5eec5e5a321a5 ]

The scpi hwmon shows the sub-zero temperature in an unsigned integer,
which would confuse the users when the machine works in low temperature
environment. This shows the sub-zero temperature in an signed value and
users can get it properly from sensors.

Signed-off-by: Riwen Lu <luriwen@kylinos.cn>
Tested-by: Xin Chen <chenxin@kylinos.cn>
Link: https://lore.kernel.org/r/20210604030959.736379-1-luriwen@kylinos.cn
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/hwmon/scpi-hwmon.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/hwmon/scpi-hwmon.c b/drivers/hwmon/scpi-hwmon.c
index 7e49da50bc69..562f3e287297 100644
--- a/drivers/hwmon/scpi-hwmon.c
+++ b/drivers/hwmon/scpi-hwmon.c
@@ -107,6 +107,15 @@ scpi_show_sensor(struct device *dev, struct device_attribute *attr, char *buf)
 
 	scpi_scale_reading(&value, sensor);
 
+	/*
+	 * Temperature sensor values are treated as signed values based on
+	 * observation even though that is not explicitly specified, and
+	 * because an unsigned u64 temperature does not really make practical
+	 * sense especially when the temperature is below zero degrees Celsius.
+	 */
+	if (sensor->info.class == TEMPERATURE)
+		return sprintf(buf, "%lld\n", (s64)value);
+
 	return sprintf(buf, "%llu\n", value);
 }
 
-- 
2.30.2