After a recent change in clang to expose uninitialized warnings from
const variables [1], there is a warning from the if statement in
advisor_mode_show().
mm/ksm.c:3687:11: error: variable 'output' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
3687 | else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/ksm.c:3690:33: note: uninitialized use occurs here
3690 | return sysfs_emit(buf, "%s\n", output);
| ^~~~~~
Rewrite the if statement to implicitly make KSM_ADVISOR_NONE the else
branch so that it is obvious to the compiler that ksm_advisor can only
be KSM_ADVISOR_NONE or KSM_ADVISOR_SCAN_TIME due to the assignments in
advisor_mode_store().
Cc: stable(a)vger.kernel.org
Fixes: 66790e9a735b ("mm/ksm: add sysfs knobs for advisor")
Closes: https://github.com/ClangBuiltLinux/linux/issues/2100
Link: https://github.com/llvm/llvm-project/commit/2464313eef01c5b1edf0eccf57a32cd… [1]
Signed-off-by: Nathan Chancellor <nathan(a)kernel.org>
---
mm/ksm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/ksm.c b/mm/ksm.c
index 2b0210d41c55..160787bb121c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3682,10 +3682,10 @@ static ssize_t advisor_mode_show(struct kobject *kobj,
{
const char *output;
- if (ksm_advisor == KSM_ADVISOR_NONE)
- output = "[none] scan-time";
- else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
+ if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
output = "none [scan-time]";
+ else
+ output = "[none] scan-time";
return sysfs_emit(buf, "%s\n", output);
}
---
base-commit: fed48693bdfeca666f7536ba88a05e9a4e5523b6
change-id: 20250715-ksm-fix-clang-21-uninit-warning-bea5a6b886ce
Best regards,
--
Nathan Chancellor <nathan(a)kernel.org>
The patch titled
Subject: mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Nathan Chancellor <nathan(a)kernel.org>
Subject: mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show()
Date: Tue, 15 Jul 2025 12:56:16 -0700
After a recent change in clang to expose uninitialized warnings from const
variables [1], there is a false positive warning from the if statement in
advisor_mode_show().
mm/ksm.c:3687:11: error: variable 'output' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
3687 | else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/ksm.c:3690:33: note: uninitialized use occurs here
3690 | return sysfs_emit(buf, "%s\n", output);
| ^~~~~~
Rewrite the if statement to implicitly make KSM_ADVISOR_NONE the else
branch so that it is obvious to the compiler that ksm_advisor can only be
KSM_ADVISOR_NONE or KSM_ADVISOR_SCAN_TIME due to the assignments in
advisor_mode_store().
Link: https://lkml.kernel.org/r/20250715-ksm-fix-clang-21-uninit-warning-v1-1-f44…
Fixes: 66790e9a735b ("mm/ksm: add sysfs knobs for advisor")
Signed-off-by: Nathan Chancellor <nathan(a)kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2100
Link: https://github.com/llvm/llvm-project/commit/2464313eef01c5b1edf0eccf57a32cd… [1]
Cc: Chengming Zhou <chengming.zhou(a)linux.dev>
Cc: David Hildenbrand <david(a)redhat.com>
Cc: Stefan Roesch <shr(a)devkernel.io>
Cc: xu xin <xu.xin16(a)zte.com.cn>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/ksm.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/ksm.c~mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show
+++ a/mm/ksm.c
@@ -3669,10 +3669,10 @@ static ssize_t advisor_mode_show(struct
{
const char *output;
- if (ksm_advisor == KSM_ADVISOR_NONE)
- output = "[none] scan-time";
- else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
+ if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
output = "none [scan-time]";
+ else
+ output = "[none] scan-time";
return sysfs_emit(buf, "%s\n", output);
}
_
Patches currently in -mm which might be from nathan(a)kernel.org are
mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show.patch
panic-add-panic_sys_info-sysctl-to-take-human-readable-string-parameter-fix.patch
From: Ge Yang <yangge1116(a)126.com>
Since commit d228814b1913 ("efi/libstub: Add get_event_log() support
for CC platforms") reuses TPM2 support code for the CC platforms, when
launching a TDX virtual machine with coco measurement enabled, the
following error log is generated:
[Firmware Bug]: Failed to parse event in TPM Final Events Log
Call Trace:
efi_config_parse_tables()
efi_tpm_eventlog_init()
tpm2_calc_event_log_size()
__calc_tpm2_event_size()
The pcr_idx value in the Intel TDX log header is 1, causing the function
__calc_tpm2_event_size() to fail to recognize the log header, ultimately
leading to the "Failed to parse event in TPM Final Events Log" error.
Intel misread the spec and wrongly sets pcrIndex to 1 in the header and
since they did this, we fear others might, so we're relaxing the header
check. There's no danger of this causing problems because we check for
the TCG_SPECID_SIG signature as the next thing.
Fixes: d228814b1913 ("efi/libstub: Add get_event_log() support for CC platforms")
Signed-off-by: Ge Yang <yangge1116(a)126.com>
Cc: stable(a)vger.kernel.org
---
V6:
- improve commit message suggested by James
V5:
- remove the pcr_index check without adding any replacement checks suggested by James and Sathyanarayanan
V4:
- remove cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) suggested by Ard
V3:
- fix build error
V2:
- limit the fix for CC only suggested by Jarkko and Sathyanarayanan
include/linux/tpm_eventlog.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
index 891368e..05c0ae5 100644
--- a/include/linux/tpm_eventlog.h
+++ b/include/linux/tpm_eventlog.h
@@ -202,8 +202,7 @@ static __always_inline u32 __calc_tpm2_event_size(struct tcg_pcr_event2_head *ev
event_type = event->event_type;
/* Verify that it's the log header */
- if (event_header->pcr_idx != 0 ||
- event_header->event_type != NO_ACTION ||
+ if (event_header->event_type != NO_ACTION ||
memcmp(event_header->digest, zero_digest, sizeof(zero_digest))) {
size = 0;
goto out;
--
2.7.4
From: "Borislav Petkov (AMD)" <bp(a)alien8.de>
VERW_CLEAR is supposed to be set only by the hypervisor to denote TSA
mitigation support to a guest. SQ_NO and L1_NO are both synthesizable,
and are going to be set by hw CPUID on future machines.
So keep the kvm_cpu_cap_init_kvm_defined() invocation *and* set them
when synthesized.
This fix is stable-only.
Co-developed-by: Jinpu Wang <jinpu.wang(a)ionos.com>
Signed-off-by: Jinpu Wang <jinpu.wang(a)ionos.com>
Signed-off-by: Borislav Petkov (AMD) <bp(a)alien8.de>
---
arch/x86/kvm/cpuid.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 02196db26a08..8f587c5bb6bc 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -822,6 +822,7 @@ void kvm_set_cpu_caps(void)
kvm_cpu_cap_check_and_set(X86_FEATURE_SBPB);
kvm_cpu_cap_check_and_set(X86_FEATURE_IBPB_BRTYPE);
kvm_cpu_cap_check_and_set(X86_FEATURE_SRSO_NO);
+ kvm_cpu_cap_check_and_set(X86_FEATURE_VERW_CLEAR);
kvm_cpu_cap_init_kvm_defined(CPUID_8000_0022_EAX,
F(PERFMON_V2)
@@ -831,6 +832,9 @@ void kvm_set_cpu_caps(void)
F(TSA_SQ_NO) | F(TSA_L1_NO)
);
+ kvm_cpu_cap_check_and_set(X86_FEATURE_TSA_SQ_NO);
+ kvm_cpu_cap_check_and_set(X86_FEATURE_TSA_L1_NO);
+
/*
* Synthesize "LFENCE is serializing" into the AMD-defined entry in
* KVM's supported CPUID if the feature is reported as supported by the
--
2.43.0
This reverts commit e8afa1557f4f963c9a511bd2c6074a941c308685.
The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.
Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.
Hence, this revert to going back to using .import_attach->dmabuf.
v3:
- cc stable
Signed-off-by: Thomas Zimmermann <tzimmermann(a)suse.de>
Reviewed-by: Simona Vetter <simona.vetter(a)ffwll.ch>
Acked-by: Christian König <christian.koenig(a)amd.com>
Cc: <stable(a)vger.kernel.org> # v6.15+
---
drivers/gpu/drm/drm_gem_dma_helper.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_gem_dma_helper.c b/drivers/gpu/drm/drm_gem_dma_helper.c
index b7f033d4352a..4f0320df858f 100644
--- a/drivers/gpu/drm/drm_gem_dma_helper.c
+++ b/drivers/gpu/drm/drm_gem_dma_helper.c
@@ -230,7 +230,7 @@ void drm_gem_dma_free(struct drm_gem_dma_object *dma_obj)
if (drm_gem_is_imported(gem_obj)) {
if (dma_obj->vaddr)
- dma_buf_vunmap_unlocked(gem_obj->dma_buf, &map);
+ dma_buf_vunmap_unlocked(gem_obj->import_attach->dmabuf, &map);
drm_prime_gem_destroy(gem_obj, dma_obj->sgt);
} else if (dma_obj->vaddr) {
if (dma_obj->map_noncoherent)
--
2.50.0
This reverts commit 1a148af06000e545e714fe3210af3d77ff903c11.
The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.
Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.
Hence, this revert to going back to using .import_attach->dmabuf.
v3:
- cc stable
Signed-off-by: Thomas Zimmermann <tzimmermann(a)suse.de>
Reviewed-by: Simona Vetter <simona.vetter(a)ffwll.ch>
Acked-by: Christian König <christian.koenig(a)amd.com>
Cc: <stable(a)vger.kernel.org> # v6.15+
---
drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 8ac0b1fa5287..5d1349c34afd 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -351,7 +351,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem,
dma_resv_assert_held(obj->resv);
if (drm_gem_is_imported(obj)) {
- ret = dma_buf_vmap(obj->dma_buf, map);
+ ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
} else {
pgprot_t prot = PAGE_KERNEL;
@@ -413,7 +413,7 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
dma_resv_assert_held(obj->resv);
if (drm_gem_is_imported(obj)) {
- dma_buf_vunmap(obj->dma_buf, map);
+ dma_buf_vunmap(obj->import_attach->dmabuf, map);
} else {
dma_resv_assert_held(shmem->base.resv);
--
2.50.0
This reverts commit cce16fcd7446dcff7480cd9d2b6417075ed81065.
The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.
Workarounds in commit 5307dce878d4 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9afc751 ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.
Hence, this revert to going back to using .import_attach->dmabuf.
v3:
- cc stable
Signed-off-by: Thomas Zimmermann <tzimmermann(a)suse.de>
Reviewed-by: Simona Vetter <simona.vetter(a)ffwll.ch>
Acked-by: Christian König <christian.koenig(a)amd.com>
Cc: <stable(a)vger.kernel.org> # v6.15+
---
drivers/gpu/drm/drm_gem_framebuffer_helper.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index 618ce725cd75..fefb2a0f6b40 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -420,6 +420,7 @@ EXPORT_SYMBOL(drm_gem_fb_vunmap);
static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_data_direction dir,
unsigned int num_planes)
{
+ struct dma_buf_attachment *import_attach;
struct drm_gem_object *obj;
int ret;
@@ -428,9 +429,10 @@ static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_dat
obj = drm_gem_fb_get_obj(fb, num_planes);
if (!obj)
continue;
+ import_attach = obj->import_attach;
if (!drm_gem_is_imported(obj))
continue;
- ret = dma_buf_end_cpu_access(obj->dma_buf, dir);
+ ret = dma_buf_end_cpu_access(import_attach->dmabuf, dir);
if (ret)
drm_err(fb->dev, "dma_buf_end_cpu_access(%u, %d) failed: %d\n",
ret, num_planes, dir);
@@ -453,6 +455,7 @@ static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_dat
*/
int drm_gem_fb_begin_cpu_access(struct drm_framebuffer *fb, enum dma_data_direction dir)
{
+ struct dma_buf_attachment *import_attach;
struct drm_gem_object *obj;
unsigned int i;
int ret;
@@ -463,9 +466,10 @@ int drm_gem_fb_begin_cpu_access(struct drm_framebuffer *fb, enum dma_data_direct
ret = -EINVAL;
goto err___drm_gem_fb_end_cpu_access;
}
+ import_attach = obj->import_attach;
if (!drm_gem_is_imported(obj))
continue;
- ret = dma_buf_begin_cpu_access(obj->dma_buf, dir);
+ ret = dma_buf_begin_cpu_access(import_attach->dmabuf, dir);
if (ret)
goto err___drm_gem_fb_end_cpu_access;
}
--
2.50.0