* FAILED: patch "[PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate allocations" failed to apply to 6.1-stable tree
@ 2026-11-07 10:52 Sasha Levin
2026-11-10 19:36 ` [PATCH 6.1.y] drm/amdkfd: fix doorbell allocation race creating duplicate allocations Sasha Levin
0 siblings, 1 reply; 2+ messages in thread
From: Sasha Levin @ 2026-11-07 10:52 UTC (permalink / raw)
To: bsdhenrymartin, felix.kuehling, alexander.deucher; +Cc: stable
The patch below does not apply to the 6.1-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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x bebad45050945a3d668d6701fb77ae2571c5d44b
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107055241-failed-6.1-bebad4505094@kernel.org' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'
Thanks,
Sasha
------------------ original commit in Linus's tree ------------------
From bebad45050945a3d668d6701fb77ae2571c5d44b Mon Sep 17 00:00:00 2001
From: Henry Martin <bsdhenrymartin@gmail.com>
Date: Sat, 10 Oct 2026 11:02:30 +0800
Subject: [PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate
allocations
The check-and-allocate sequence on pdd->qpd.proc_doorbells is
lockless at every call site of kfd_alloc_process_doorbells():
kfd_get_process_doorbells() (mmap of /dev/kfd),
kfd_ioctl_create_queue() and the CRIU restore path each test the
pointer under different locking (or none), so two racing threads can
both observe NULL and each allocate a doorbell BO and bitmap,
orphaning one allocation and handing the two mappings different
backing pages.
Move the serialization into kfd_alloc_process_doorbells() itself,
using a new per-process-device mutex so all three call sites are
covered regardless of their own locking. The device-global
kfd->doorbell_mutex is not suitable here: it is acquired under
dqm->lock on the kernel-doorbell path (start_cpsch() -> pm_init() ->
kq_initialize() -> kfd_get_kernel_doorbell()), so holding it across
the sleeping allocations above would create a lock-ordering
inversion with dqm->lock via TTM eviction, and it would also
serialize doorbell setup of unrelated processes behind a
device-wide lock for per-process state.
This issue was discovered by Tencent CodeBuddy Security.
v3 (Felix Kuehling):
- Removed unlocked check in kfd_get_process_doorbell flagged as
problematic by Sashiko Bot. Fall back to the locked check inside
kfd_alloc_process_doorbells
- Added missing mutex_destroy
v4 (Felix Kuehling):
- Removed unlocked checks around other kfd_alloc_process_doorbells calls
Fixes: 16f0013157bf ("drm/amdkfd: Allocate doorbells only when needed")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
Signed-off-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4e27ba5ad5f76932d4f6cbacd25c81c2dd40ec4a)
Cc: stable@vger.kernel.org
---
drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 18 +++++++-----------
drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c | 23 +++++++++++++++++------
drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 3 +++
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 ++
4 files changed, 29 insertions(+), 17 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index 344da6c0e96ad..3081d9aaf053a 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -427,12 +427,10 @@ static int kfd_ioctl_create_queue(struct file *filep, struct kfd_process *p,
}
}
- if (!pdd->qpd.proc_doorbells) {
- err = kfd_alloc_process_doorbells(dev->kfd, pdd);
- if (err) {
- pr_debug("failed to allocate process doorbells\n");
- goto err_bind_process;
- }
+ err = kfd_alloc_process_doorbells(dev->kfd, pdd);
+ if (err) {
+ pr_debug("failed to allocate process doorbells\n");
+ goto err_bind_process;
}
err = kfd_queue_acquire_buffers(pdd, &q_properties);
@@ -2455,11 +2453,9 @@ static int criu_restore_devices(struct kfd_process *p,
goto exit;
}
- if (!pdd->qpd.proc_doorbells) {
- ret = kfd_alloc_process_doorbells(dev->kfd, pdd);
- if (ret)
- goto exit;
- }
+ ret = kfd_alloc_process_doorbells(dev->kfd, pdd);
+ if (ret)
+ goto exit;
}
/*
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
index fdcf7f2d1b5b4..6af268a031f22 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
@@ -239,11 +239,9 @@ phys_addr_t kfd_get_process_doorbells(struct kfd_process_device *pdd)
struct amdgpu_device *adev = pdd->dev->adev;
uint32_t first_db_index;
- if (!pdd->qpd.proc_doorbells) {
- if (kfd_alloc_process_doorbells(pdd->dev->kfd, pdd))
- /* phys_addr_t 0 is error */
- return 0;
- }
+ if (kfd_alloc_process_doorbells(pdd->dev->kfd, pdd))
+ /* phys_addr_t 0 is error */
+ return 0;
first_db_index = amdgpu_doorbell_index_on_bar(adev,
pdd->qpd.proc_doorbells,
@@ -257,12 +255,21 @@ int kfd_alloc_process_doorbells(struct kfd_dev *kfd, struct kfd_process_device *
int r;
struct qcm_process_device *qpd = &pdd->qpd;
+ mutex_lock(&pdd->doorbell_mutex);
+
+ /* Another thread may have won the check-and-allocate race */
+ if (qpd->proc_doorbells) {
+ mutex_unlock(&pdd->doorbell_mutex);
+ return 0;
+ }
+
/* Allocate bitmap for dynamic doorbell allocation */
qpd->doorbell_bitmap = bitmap_zalloc(KFD_MAX_NUM_OF_QUEUES_PER_PROCESS,
GFP_KERNEL);
if (!qpd->doorbell_bitmap) {
DRM_ERROR("Failed to allocate process doorbell bitmap\n");
- return -ENOMEM;
+ r = -ENOMEM;
+ goto unlock;
}
r = init_doorbell_bitmap(&pdd->qpd, kfd);
@@ -284,11 +291,15 @@ int kfd_alloc_process_doorbells(struct kfd_dev *kfd, struct kfd_process_device *
DRM_ERROR("Failed to allocate process doorbells\n");
goto err;
}
+
+ mutex_unlock(&pdd->doorbell_mutex);
return 0;
err:
bitmap_free(qpd->doorbell_bitmap);
qpd->doorbell_bitmap = NULL;
+unlock:
+ mutex_unlock(&pdd->doorbell_mutex);
return r;
}
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index b9a31489b1c89..e102086ac49a8 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -784,6 +784,9 @@ struct kfd_process_device {
/* per-process-per device QCM data structure */
struct qcm_process_device qpd;
+ /* Serializes process doorbell allocation for this device */
+ struct mutex doorbell_mutex;
+
/*Apertures*/
uint64_t lds_base;
uint64_t lds_limit;
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index 226f52626e849..51b0df4984945 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1233,6 +1233,7 @@ static void kfd_process_destroy_pdds(struct kfd_process *p)
}
atomic_dec(&pdd->dev->kfd->kfd_processes_count);
+ mutex_destroy(&pdd->doorbell_mutex);
kfree(pdd);
p->pdds[i] = NULL;
@@ -1802,6 +1803,7 @@ struct kfd_process_device *kfd_create_process_device_data(struct kfd_node *dev,
pdd->dev = dev;
INIT_LIST_HEAD(&pdd->qpd.queues_list);
INIT_LIST_HEAD(&pdd->qpd.priv_queue_list);
+ mutex_init(&pdd->doorbell_mutex);
pdd->qpd.dqm = dev->dqm;
pdd->qpd.pqm = &p->pqm;
pdd->qpd.evicted = 0;
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH 6.1.y] drm/amdkfd: fix doorbell allocation race creating duplicate allocations
2026-11-07 10:52 FAILED: patch "[PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate allocations" failed to apply to 6.1-stable tree Sasha Levin
@ 2026-11-10 19:36 ` Sasha Levin
0 siblings, 0 replies; 2+ messages in thread
From: Sasha Levin @ 2026-11-10 19:36 UTC (permalink / raw)
To: stable; +Cc: Henry Martin, Felix Kuehling, Alex Deucher, Sasha Levin
From: Henry Martin <bsdhenrymartin@gmail.com>
[ Upstream commit bebad45050945a3d668d6701fb77ae2571c5d44b ]
The check-and-allocate sequence on pdd->qpd.proc_doorbells is
lockless at every call site of kfd_alloc_process_doorbells():
kfd_get_process_doorbells() (mmap of /dev/kfd),
kfd_ioctl_create_queue() and the CRIU restore path each test the
pointer under different locking (or none), so two racing threads can
both observe NULL and each allocate a doorbell BO and bitmap,
orphaning one allocation and handing the two mappings different
backing pages.
Move the serialization into kfd_alloc_process_doorbells() itself,
using a new per-process-device mutex so all three call sites are
covered regardless of their own locking. The device-global
kfd->doorbell_mutex is not suitable here: it is acquired under
dqm->lock on the kernel-doorbell path (start_cpsch() -> pm_init() ->
kq_initialize() -> kfd_get_kernel_doorbell()), so holding it across
the sleeping allocations above would create a lock-ordering
inversion with dqm->lock via TTM eviction, and it would also
serialize doorbell setup of unrelated processes behind a
device-wide lock for per-process state.
This issue was discovered by Tencent CodeBuddy Security.
v3 (Felix Kuehling):
- Removed unlocked check in kfd_get_process_doorbell flagged as
problematic by Sashiko Bot. Fall back to the locked check inside
kfd_alloc_process_doorbells
- Added missing mutex_destroy
v4 (Felix Kuehling):
- Removed unlocked checks around other kfd_alloc_process_doorbells calls
Fixes: 16f0013157bf ("drm/amdkfd: Allocate doorbells only when needed")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
Signed-off-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 4e27ba5ad5f76932d4f6cbacd25c81c2dd40ec4a)
Cc: stable@vger.kernel.org
[ sashal: Adapted doorbell allocation locking for numeric indices instead of buffer objects. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 6 ++---
drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c | 23 +++++++++++--------
drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 5 +++-
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 3 +++
.../amd/amdkfd/kfd_process_queue_manager.c | 3 +--
5 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index 43bfd668c5480..a08c84556ace4 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -333,8 +333,7 @@ static int kfd_ioctl_create_queue(struct file *filep, struct kfd_process *p,
goto err_bind_process;
}
- if (!pdd->doorbell_index &&
- kfd_alloc_process_doorbells(dev, &pdd->doorbell_index) < 0) {
+ if (kfd_alloc_process_doorbells(dev, pdd) < 0) {
err = -ENOMEM;
goto err_alloc_doorbells;
}
@@ -2203,8 +2202,7 @@ static int criu_restore_devices(struct kfd_process *p,
goto exit;
}
- if (!pdd->doorbell_index &&
- kfd_alloc_process_doorbells(pdd->dev, &pdd->doorbell_index) < 0) {
+ if (kfd_alloc_process_doorbells(pdd->dev, pdd) < 0) {
ret = -ENOMEM;
goto exit;
}
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
index 3ac599f74fea8..a38e3e917c437 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_doorbell.c
@@ -277,35 +277,40 @@ uint64_t kfd_get_number_elems(struct kfd_dev *kfd)
phys_addr_t kfd_get_process_doorbells(struct kfd_process_device *pdd)
{
- if (!pdd->doorbell_index) {
- int r = kfd_alloc_process_doorbells(pdd->dev,
- &pdd->doorbell_index);
- if (r < 0)
- return 0;
- }
+ if (kfd_alloc_process_doorbells(pdd->dev, pdd) < 0)
+ return 0;
return pdd->dev->doorbell_base +
pdd->doorbell_index * kfd_doorbell_process_slice(pdd->dev);
}
-int kfd_alloc_process_doorbells(struct kfd_dev *kfd, unsigned int *doorbell_index)
+int kfd_alloc_process_doorbells(struct kfd_dev *kfd, struct kfd_process_device *pdd)
{
int r = 0;
+ mutex_lock(&pdd->doorbell_mutex);
+
+ /* Another thread may have won the check-and-allocate race */
+ if (pdd->doorbell_index) {
+ mutex_unlock(&pdd->doorbell_mutex);
+ return 0;
+ }
+
if (!kfd->shared_resources.enable_mes)
r = ida_simple_get(&kfd->doorbell_ida, 1,
kfd->max_doorbell_slices, GFP_KERNEL);
else
r = amdgpu_mes_alloc_process_doorbells(
(struct amdgpu_device *)kfd->adev,
- doorbell_index);
+ &pdd->doorbell_index);
if (r > 0)
- *doorbell_index = r;
+ pdd->doorbell_index = r;
if (r < 0)
pr_err("Failed to allocate process doorbells\n");
+ mutex_unlock(&pdd->doorbell_mutex);
return r;
}
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index cdcaba185052c..04f8098b8ba3d 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -712,6 +712,9 @@ struct kfd_process_device {
/* per-process-per device QCM data structure */
struct qcm_process_device qpd;
+ /* Serializes process doorbell allocation for this device */
+ struct mutex doorbell_mutex;
+
/*Apertures*/
uint64_t lds_base;
uint64_t lds_limit;
@@ -1017,7 +1020,7 @@ unsigned int kfd_get_doorbell_dw_offset_in_bar(struct kfd_dev *kfd,
unsigned int doorbell_id);
phys_addr_t kfd_get_process_doorbells(struct kfd_process_device *pdd);
int kfd_alloc_process_doorbells(struct kfd_dev *kfd,
- unsigned int *doorbell_index);
+ struct kfd_process_device *pdd);
void kfd_free_process_doorbells(struct kfd_dev *kfd,
unsigned int doorbell_index);
/* GTT Sub-Allocator */
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index fd7fecaa9254b..db0689c23e6ad 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1065,6 +1065,8 @@ static void kfd_process_destroy_pdds(struct kfd_process *p)
pdd->runtime_inuse = false;
}
+ mutex_destroy(&pdd->doorbell_mutex);
+
kfree(pdd);
p->pdds[i] = NULL;
}
@@ -1613,6 +1615,7 @@ struct kfd_process_device *kfd_create_process_device_data(struct kfd_dev *dev,
memset(pdd->proc_ctx_cpu_ptr, 0, AMDGPU_MES_PROC_CTX_SIZE);
}
+ mutex_init(&pdd->doorbell_mutex);
p->pdds[p->n_pdds++] = pdd;
/* Init idr used for memory handle translation */
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
index 7c85bb9e270e7..b28b15e2d14c1 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
@@ -868,8 +868,7 @@ int kfd_criu_restore_queue(struct kfd_process *p,
*priv_data_offset += q_extra_data_size;
- if (!pdd->doorbell_index &&
- kfd_alloc_process_doorbells(pdd->dev, &pdd->doorbell_index) < 0) {
+ if (kfd_alloc_process_doorbells(pdd->dev, pdd) < 0) {
ret = -ENOMEM;
goto exit;
}
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-11-10 19:36 UTC | newest]
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2026-11-07 10:52 FAILED: patch "[PATCH] drm/amdkfd: fix doorbell allocation race creating duplicate allocations" failed to apply to 6.1-stable tree Sasha Levin
2026-11-10 19:36 ` [PATCH 6.1.y] drm/amdkfd: fix doorbell allocation race creating duplicate allocations Sasha Levin
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