refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
arch/x86/kernel/tboot.c | 2 +-
drivers/firmware/efi/arm-runtime.c | 2 +-
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 +-
drivers/gpu/drm/i915/i915_gem_userptr.c | 1 -
fs/proc/base.c | 8 --------
fs/userfaultfd.c | 3 +--
include/linux/mm_types.h | 2 +-
include/linux/sched.h | 6 +++---
kernel/fork.c | 2 +-
mm/debug.c | 2 +-
mm/init-mm.c | 2 +-
mm/mmu_notifier.c | 6 +++---
12 files changed, 14 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 39aaca5..fdbae72 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -103,7 +103,7 @@ static struct mm_struct tboot_mm = {
.mm_rb = RB_ROOT,
.pgd = swapper_pg_dir,
.mm_users = REFCOUNT_INIT(2),
- .mm_count = ATOMIC_INIT(1),
+ .mm_count = REFCOUNT_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 23e41f9..f0571f2 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -33,7 +33,7 @@ extern u64 efi_system_table;
static struct mm_struct efi_mm = {
.mm_rb = RB_ROOT,
.mm_users = REFCOUNT_INIT(2),
- .mm_count = ATOMIC_INIT(1),
+ .mm_count = REFCOUNT_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(efi_mm.mmap_sem),
.page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index ca5f2aa..d86ceec 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -204,7 +204,7 @@ static void kfd_process_destroy_delayed(struct rcu_head *rcu)
BUG_ON(!kfd_process_wq);
p = container_of(rcu, struct kfd_process, rcu);
- BUG_ON(atomic_read(&p->mm->mm_count) <= 0);
+ BUG_ON(refcount_read(&p->mm->mm_count) == 0);
mmdrop(p->mm);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 0115989..68fb396 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -335,7 +335,6 @@ i915_gem_userptr_init__mm_struct(struct drm_i915_gem_object *obj)
mm->mm = current->mm;
mmgrab(current->mm);
-
mm->mn = NULL;
/* Protected by dev_priv->mm_lock */
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a75dca3..445b259 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -921,11 +921,7 @@ static ssize_t environ_read(struct file *file, char __user *buf,
return -ENOMEM;
ret = 0;
-<<<<<<< e5c2d109eae88b7c203d396dfaeb284f95f6ffe5
if (!mmget_not_zero(mm))
-=======
- if (!refcount_inc_not_zero(&mm->mm_users))
->>>>>>> mm: convert mm_struct.mm_users from atomic_t to refcount_t
goto free;
down_read(&mm->mmap_sem);
@@ -1068,11 +1064,7 @@ static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
if (p) {
if (refcount_read(&p->mm->mm_users) > 1) {
mm = p->mm;
-<<<<<<< e5c2d109eae88b7c203d396dfaeb284f95f6ffe5
mmgrab(mm);
-=======
- refcount_inc(&mm->mm_count);
->>>>>>> mm: convert mm_struct.mm_users from atomic_t to refcount_t
}
task_unlock(p);
}
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 3c421d0..1fd19ac 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -613,7 +613,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
ctx->features = octx->features;
ctx->released = false;
ctx->mm = vma->vm_mm;
- atomic_inc(&ctx->mm->mm_count);
+ mmgrab(ctx->mm);
userfaultfd_ctx_get(octx);
fctx->orig = octx;
@@ -1848,7 +1848,6 @@ static struct file *userfaultfd_file_create(int flags)
ctx->mm = current->mm;
/* prevent the mm struct to be freed */
mmgrab(ctx->mm);
-
file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
if (IS_ERR(file)) {
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index af260d6..6445c58 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -427,7 +427,7 @@ struct mm_struct {
* Use mmgrab()/mmdrop() to modify. When this drops to 0, the
* &struct mm_struct is freed.
*/
- atomic_t mm_count;
+ refcount_t mm_count;
atomic_long_t nr_ptes; /* PTE page table pages */
#if CONFIG_PGTABLE_LEVELS > 2
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c21682c..41a2e52 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2924,14 +2924,14 @@ extern struct mm_struct * mm_alloc(void);
*/
static inline void mmgrab(struct mm_struct *mm)
{
- atomic_inc(&mm->mm_count);
+ refcount_inc(&mm->mm_count);
}
/* mmdrop drops the mm and the page tables */
extern void __mmdrop(struct mm_struct *);
static inline void mmdrop(struct mm_struct *mm)
{
- if (unlikely(atomic_dec_and_test(&mm->mm_count)))
+ if (unlikely(refcount_dec_and_test(&mm->mm_count)))
__mmdrop(mm);
}
@@ -2943,7 +2943,7 @@ static inline void mmdrop_async_fn(struct work_struct *work)
static inline void mmdrop_async(struct mm_struct *mm)
{
- if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
+ if (unlikely(refcount_dec_and_test(&mm->mm_count))) {
INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
schedule_work(&mm->async_put_work);
}
diff --git a/kernel/fork.c b/kernel/fork.c
index 60ff801..31c887c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -760,7 +760,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm->mm_rb = RB_ROOT;
mm->vmacache_seqnum = 0;
refcount_set(&mm->mm_users, 1);
- atomic_set(&mm->mm_count, 1);
+ refcount_set(&mm->mm_count, 1);
init_rwsem(&mm->mmap_sem);
INIT_LIST_HEAD(&mm->mmlist);
mm->core_state = NULL;
diff --git a/mm/debug.c b/mm/debug.c
index 0866505..eebbd15 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -135,7 +135,7 @@ void dump_mm(const struct mm_struct *mm)
#endif
mm->mmap_base, mm->mmap_legacy_base, mm->highest_vm_end,
mm->pgd, refcount_read(&mm->mm_users),
- atomic_read(&mm->mm_count),
+ refcount_read(&mm->mm_count),
atomic_long_read((atomic_long_t *)&mm->nr_ptes),
mm_nr_pmds((struct mm_struct *)mm),
mm->map_count,
diff --git a/mm/init-mm.c b/mm/init-mm.c
index 6927a72..8de5267 100644
--- a/mm/init-mm.c
+++ b/mm/init-mm.c
@@ -18,7 +18,7 @@ struct mm_struct init_mm = {
.mm_rb = RB_ROOT,
.pgd = swapper_pg_dir,
.mm_users = REFCOUNT_INIT(2),
- .mm_count = ATOMIC_INIT(1),
+ .mm_count = REFCOUNT_INIT(1),
.mmap_sem = __RWSEM_INITIALIZER(init_mm.mmap_sem),
.page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock),
.mmlist = LIST_HEAD_INIT(init_mm.mmlist),
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index d8c11e1..d179083 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -348,7 +348,7 @@ void __mmu_notifier_mm_destroy(struct mm_struct *mm)
*/
void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
{
- BUG_ON(atomic_read(&mm->mm_count) <= 0);
+ BUG_ON(refcount_read(&mm->mm_count) <= 0);
if (!hlist_unhashed(&mn->hlist)) {
/*
@@ -381,7 +381,7 @@ void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
*/
synchronize_srcu(&srcu);
- BUG_ON(atomic_read(&mm->mm_count) <= 0);
+ BUG_ON(refcount_read(&mm->mm_count) <= 0);
mmdrop(mm);
}
@@ -401,7 +401,7 @@ void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
hlist_del_init_rcu(&mn->hlist);
spin_unlock(&mm->mmu_notifier_mm->lock);
- BUG_ON(atomic_read(&mm->mm_count) <= 0);
+ BUG_ON(refcount_read(&mm->mm_count) <= 0);
mmdrop(mm);
}
EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
--
2.7.4
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