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drm/amdkfd: Don't dereference kfd_process.mm

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The kfd_process doesn't own a reference to the mm_struct, so it can
disappear without warning even while the kfd_process still exists.

Therefore, avoid dereferencing the kfd_process.mm pointer and make
it opaque. Use get_task_mm to get a temporary reference to the mm
when it's needed.

v2: removed unnecessary WARN_ON

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
This commit is contained in:
Felix Kuehling 2017-10-27 19:35:19 -04:00 committed by Oded Gabbay
parent 66b783b446
commit 9b56bb1154
3 changed files with 21 additions and 6 deletions
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19
drivers/gpu/drm/amd/amdkfd/kfd_events.c
View File

@ -24,8 +24,8 @@
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/memory.h>
#include "kfd_priv.h"
@ -904,14 +904,24 @@ void kfd_signal_iommu_event(struct kfd_dev *dev, unsigned int pasid,
* running so the lookup function returns a locked process.
*/
struct kfd_process *p = kfd_lookup_process_by_pasid(pasid);
struct mm_struct *mm;
if (!p)
return; /* Presumably process exited. */
/* Take a safe reference to the mm_struct, which may otherwise
* disappear even while the kfd_process is still referenced.
*/
mm = get_task_mm(p->lead_thread);
if (!mm) {
mutex_unlock(&p->mutex);
return; /* Process is exiting */
}
memset(&memory_exception_data, 0, sizeof(memory_exception_data));
down_read(&p->mm->mmap_sem);
vma = find_vma(p->mm, address);
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
memory_exception_data.gpu_id = dev->id;
memory_exception_data.va = address;
@ -937,7 +947,8 @@ void kfd_signal_iommu_event(struct kfd_dev *dev, unsigned int pasid,
}
}
up_read(&p->mm->mmap_sem);
up_read(&mm->mmap_sem);
mmput(mm);
mutex_lock(&p->event_mutex);

7
drivers/gpu/drm/amd/amdkfd/kfd_priv.h
View File

@ -494,7 +494,12 @@ struct kfd_process {
*/
struct hlist_node kfd_processes;
struct mm_struct *mm;
/*
* Opaque pointer to mm_struct. We don't hold a reference to
* it so it should never be dereferenced from here. This is
* only used for looking up processes by their mm.
*/
void *mm;
struct mutex mutex;

1
drivers/gpu/drm/amd/amdkfd/kfd_process.c
View File

@ -200,7 +200,6 @@ static void kfd_process_destroy_delayed(struct rcu_head *rcu)
struct kfd_process *p;
p = container_of(rcu, struct kfd_process, rcu);
WARN_ON(atomic_read(&p->mm->mm_count) <= 0);
mmdrop(p->mm);