Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY
ioctl are moved into a separate structure. In the next patch this allows
ioctl to reuse some of the functions used for reading /proc/pid/maps
without using file->private_data. This prevents concurrent modification
of file->private_data members by ioctl and /proc/pid/maps readers.

The change is pure code refactoring and has no functional changes.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
---
 fs/proc/internal.h   | 15 ++++++----
 fs/proc/task_mmu.c   | 70 ++++++++++++++++++++++----------------------
 fs/proc/task_nommu.c | 14 ++++-----
 3 files changed, 52 insertions(+), 47 deletions(-)

diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index e737401d7383..d1598576506c 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -378,16 +378,21 @@ extern void proc_self_init(void);
  * task_[no]mmu.c
  */
 struct mem_size_stats;
-struct proc_maps_private {
-	struct inode *inode;
-	struct task_struct *task;
+
+struct proc_maps_locking_ctx {
 	struct mm_struct *mm;
-	struct vma_iterator iter;
-	loff_t last_pos;
 #ifdef CONFIG_PER_VMA_LOCK
 	bool mmap_locked;
 	struct vm_area_struct *locked_vma;
 #endif
+};
+
+struct proc_maps_private {
+	struct inode *inode;
+	struct task_struct *task;
+	struct vma_iterator iter;
+	loff_t last_pos;
+	struct proc_maps_locking_ctx lock_ctx;
 #ifdef CONFIG_NUMA
 	struct mempolicy *task_mempolicy;
 #endif
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ee1e4ccd33bd..45134335e086 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -132,11 +132,11 @@ static void release_task_mempolicy(struct proc_maps_private *priv)
 
 #ifdef CONFIG_PER_VMA_LOCK
 
-static void unlock_vma(struct proc_maps_private *priv)
+static void unlock_vma(struct proc_maps_locking_ctx *lock_ctx)
 {
-	if (priv->locked_vma) {
-		vma_end_read(priv->locked_vma);
-		priv->locked_vma = NULL;
+	if (lock_ctx->locked_vma) {
+		vma_end_read(lock_ctx->locked_vma);
+		lock_ctx->locked_vma = NULL;
 	}
 }
 
@@ -151,14 +151,14 @@ static inline bool lock_vma_range(struct seq_file *m,
 	 * walking the vma tree under rcu read protection.
 	 */
 	if (m->op != &proc_pid_maps_op) {
-		if (mmap_read_lock_killable(priv->mm))
+		if (mmap_read_lock_killable(priv->lock_ctx.mm))
 			return false;
 
-		priv->mmap_locked = true;
+		priv->lock_ctx.mmap_locked = true;
 	} else {
 		rcu_read_lock();
-		priv->locked_vma = NULL;
-		priv->mmap_locked = false;
+		priv->lock_ctx.locked_vma = NULL;
+		priv->lock_ctx.mmap_locked = false;
 	}
 
 	return true;
@@ -166,10 +166,10 @@ static inline bool lock_vma_range(struct seq_file *m,
 
 static inline void unlock_vma_range(struct proc_maps_private *priv)
 {
-	if (priv->mmap_locked) {
-		mmap_read_unlock(priv->mm);
+	if (priv->lock_ctx.mmap_locked) {
+		mmap_read_unlock(priv->lock_ctx.mm);
 	} else {
-		unlock_vma(priv);
+		unlock_vma(&priv->lock_ctx);
 		rcu_read_unlock();
 	}
 }
@@ -179,13 +179,13 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
 {
 	struct vm_area_struct *vma;
 
-	if (priv->mmap_locked)
+	if (priv->lock_ctx.mmap_locked)
 		return vma_next(&priv->iter);
 
-	unlock_vma(priv);
-	vma = lock_next_vma(priv->mm, &priv->iter, last_pos);
+	unlock_vma(&priv->lock_ctx);
+	vma = lock_next_vma(priv->lock_ctx.mm, &priv->iter, last_pos);
 	if (!IS_ERR_OR_NULL(vma))
-		priv->locked_vma = vma;
+		priv->lock_ctx.locked_vma = vma;
 
 	return vma;
 }
@@ -193,14 +193,14 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
 static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
 					 loff_t pos)
 {
-	if (priv->mmap_locked)
+	if (priv->lock_ctx.mmap_locked)
 		return false;
 
 	rcu_read_unlock();
-	mmap_read_lock(priv->mm);
+	mmap_read_lock(priv->lock_ctx.mm);
 	/* Reinitialize the iterator after taking mmap_lock */
 	vma_iter_set(&priv->iter, pos);
-	priv->mmap_locked = true;
+	priv->lock_ctx.mmap_locked = true;
 
 	return true;
 }
@@ -210,12 +210,12 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
 static inline bool lock_vma_range(struct seq_file *m,
 				  struct proc_maps_private *priv)
 {
-	return mmap_read_lock_killable(priv->mm) == 0;
+	return mmap_read_lock_killable(priv->lock_ctx.mm) == 0;
 }
 
 static inline void unlock_vma_range(struct proc_maps_private *priv)
 {
-	mmap_read_unlock(priv->mm);
+	mmap_read_unlock(priv->lock_ctx.mm);
 }
 
 static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
@@ -258,7 +258,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
 		*ppos = vma->vm_end;
 	} else {
 		*ppos = SENTINEL_VMA_GATE;
-		vma = get_gate_vma(priv->mm);
+		vma = get_gate_vma(priv->lock_ctx.mm);
 	}
 
 	return vma;
@@ -278,7 +278,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
 	if (!priv->task)
 		return ERR_PTR(-ESRCH);
 
-	mm = priv->mm;
+	mm = priv->lock_ctx.mm;
 	if (!mm || !mmget_not_zero(mm)) {
 		put_task_struct(priv->task);
 		priv->task = NULL;
@@ -318,7 +318,7 @@ static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
 static void m_stop(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
-	struct mm_struct *mm = priv->mm;
+	struct mm_struct *mm = priv->lock_ctx.mm;
 
 	if (!priv->task)
 		return;
@@ -339,9 +339,9 @@ static int proc_maps_open(struct inode *inode, struct file *file,
 		return -ENOMEM;
 
 	priv->inode = inode;
-	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
-	if (IS_ERR_OR_NULL(priv->mm)) {
-		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
+	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
+		int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
 
 		seq_release_private(inode, file);
 		return err;
@@ -355,8 +355,8 @@ static int proc_map_release(struct inode *inode, struct file *file)
 	struct seq_file *seq = file->private_data;
 	struct proc_maps_private *priv = seq->private;
 
-	if (priv->mm)
-		mmdrop(priv->mm);
+	if (priv->lock_ctx.mm)
+		mmdrop(priv->lock_ctx.mm);
 
 	return seq_release_private(inode, file);
 }
@@ -610,7 +610,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
 	if (!!karg.build_id_size != !!karg.build_id_addr)
 		return -EINVAL;
 
-	mm = priv->mm;
+	mm = priv->lock_ctx.mm;
 	if (!mm || !mmget_not_zero(mm))
 		return -ESRCH;
 
@@ -1311,7 +1311,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
 	struct mem_size_stats mss = {};
-	struct mm_struct *mm = priv->mm;
+	struct mm_struct *mm = priv->lock_ctx.mm;
 	struct vm_area_struct *vma;
 	unsigned long vma_start = 0, last_vma_end = 0;
 	int ret = 0;
@@ -1456,9 +1456,9 @@ static int smaps_rollup_open(struct inode *inode, struct file *file)
 		goto out_free;
 
 	priv->inode = inode;
-	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
-	if (IS_ERR_OR_NULL(priv->mm)) {
-		ret = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
+	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
+		ret = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
 
 		single_release(inode, file);
 		goto out_free;
@@ -1476,8 +1476,8 @@ static int smaps_rollup_release(struct inode *inode, struct file *file)
 	struct seq_file *seq = file->private_data;
 	struct proc_maps_private *priv = seq->private;
 
-	if (priv->mm)
-		mmdrop(priv->mm);
+	if (priv->lock_ctx.mm)
+		mmdrop(priv->lock_ctx.mm);
 
 	kfree(priv);
 	return single_release(inode, file);
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 59bfd61d653a..d362919f4f68 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -204,7 +204,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
 	if (!priv->task)
 		return ERR_PTR(-ESRCH);
 
-	mm = priv->mm;
+	mm = priv->lock_ctx.mm;
 	if (!mm || !mmget_not_zero(mm)) {
 		put_task_struct(priv->task);
 		priv->task = NULL;
@@ -226,7 +226,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
 static void m_stop(struct seq_file *m, void *v)
 {
 	struct proc_maps_private *priv = m->private;
-	struct mm_struct *mm = priv->mm;
+	struct mm_struct *mm = priv->lock_ctx.mm;
 
 	if (!priv->task)
 		return;
@@ -259,9 +259,9 @@ static int maps_open(struct inode *inode, struct file *file,
 		return -ENOMEM;
 
 	priv->inode = inode;
-	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
-	if (IS_ERR_OR_NULL(priv->mm)) {
-		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
+	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
+	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
+		int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
 
 		seq_release_private(inode, file);
 		return err;
@@ -276,8 +276,8 @@ static int map_release(struct inode *inode, struct file *file)
 	struct seq_file *seq = file->private_data;
 	struct proc_maps_private *priv = seq->private;
 
-	if (priv->mm)
-		mmdrop(priv->mm);
+	if (priv->lock_ctx.mm)
+		mmdrop(priv->lock_ctx.mm);
 
 	return seq_release_private(inode, file);
 }
-- 
2.50.1.565.gc32cd1483b-goog

On Wed, Aug 06, 2025 at 08:59:03AM -0700, Suren Baghdasaryan wrote:
> Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY
> ioctl are moved into a separate structure. In the next patch this allows
> ioctl to reuse some of the functions used for reading /proc/pid/maps
> without using file->private_data. This prevents concurrent modification
> of file->private_data members by ioctl and /proc/pid/maps readers.
>
> The change is pure code refactoring and has no functional changes.
>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> ---
>  fs/proc/internal.h   | 15 ++++++----
>  fs/proc/task_mmu.c   | 70 ++++++++++++++++++++++----------------------
>  fs/proc/task_nommu.c | 14 ++++-----
>  3 files changed, 52 insertions(+), 47 deletions(-)
>
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index e737401d7383..d1598576506c 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -378,16 +378,21 @@ extern void proc_self_init(void);
>   * task_[no]mmu.c
>   */
>  struct mem_size_stats;
> -struct proc_maps_private {
> -	struct inode *inode;
> -	struct task_struct *task;
> +
> +struct proc_maps_locking_ctx {

Decent name :)

>  	struct mm_struct *mm;
> -	struct vma_iterator iter;
> -	loff_t last_pos;
>  #ifdef CONFIG_PER_VMA_LOCK
>  	bool mmap_locked;
>  	struct vm_area_struct *locked_vma;
>  #endif
> +};
> +
> +struct proc_maps_private {
> +	struct inode *inode;
> +	struct task_struct *task;
> +	struct vma_iterator iter;
> +	loff_t last_pos;
> +	struct proc_maps_locking_ctx lock_ctx;
>  #ifdef CONFIG_NUMA
>  	struct mempolicy *task_mempolicy;
>  #endif

I was going to ask why we have these in internal.h, but then noticed we have to
have a nommu version of the task_mmu stuff for museum pieces and
why-do-they-exist arches, sigh.

> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index ee1e4ccd33bd..45134335e086 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -132,11 +132,11 @@ static void release_task_mempolicy(struct proc_maps_private *priv)
>
>  #ifdef CONFIG_PER_VMA_LOCK
>
> -static void unlock_vma(struct proc_maps_private *priv)
> +static void unlock_vma(struct proc_maps_locking_ctx *lock_ctx)
>  {
> -	if (priv->locked_vma) {
> -		vma_end_read(priv->locked_vma);
> -		priv->locked_vma = NULL;
> +	if (lock_ctx->locked_vma) {
> +		vma_end_read(lock_ctx->locked_vma);
> +		lock_ctx->locked_vma = NULL;
>  	}
>  }
>
> @@ -151,14 +151,14 @@ static inline bool lock_vma_range(struct seq_file *m,
>  	 * walking the vma tree under rcu read protection.
>  	 */
>  	if (m->op != &proc_pid_maps_op) {
> -		if (mmap_read_lock_killable(priv->mm))
> +		if (mmap_read_lock_killable(priv->lock_ctx.mm))
>  			return false;
>
> -		priv->mmap_locked = true;
> +		priv->lock_ctx.mmap_locked = true;
>  	} else {
>  		rcu_read_lock();
> -		priv->locked_vma = NULL;
> -		priv->mmap_locked = false;
> +		priv->lock_ctx.locked_vma = NULL;
> +		priv->lock_ctx.mmap_locked = false;
>  	}
>
>  	return true;
> @@ -166,10 +166,10 @@ static inline bool lock_vma_range(struct seq_file *m,
>
>  static inline void unlock_vma_range(struct proc_maps_private *priv)
>  {

Not sure why we have unlock_vma() parameterised by proc_maps_locking_ctx but
this is parameerised by proc_maps_private?

Seems more consistent to have both parameterised by proc_maps_locking_ctx.

Maybe we'd want lock() forms this way too for consistency?

> -	if (priv->mmap_locked) {
> -		mmap_read_unlock(priv->mm);
> +	if (priv->lock_ctx.mmap_locked) {
> +		mmap_read_unlock(priv->lock_ctx.mm);
>  	} else {
> -		unlock_vma(priv);
> +		unlock_vma(&priv->lock_ctx);
>  		rcu_read_unlock();
>  	}
>  }
> @@ -179,13 +179,13 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
>  {
>  	struct vm_area_struct *vma;
>

We reference priv->lock_ctx 3 times here, either extract as helper var or pass
in direct perhaps?

> -	if (priv->mmap_locked)
> +	if (priv->lock_ctx.mmap_locked)
>  		return vma_next(&priv->iter);
>
> -	unlock_vma(priv);
> -	vma = lock_next_vma(priv->mm, &priv->iter, last_pos);
> +	unlock_vma(&priv->lock_ctx);
> +	vma = lock_next_vma(priv->lock_ctx.mm, &priv->iter, last_pos);
>  	if (!IS_ERR_OR_NULL(vma))
> -		priv->locked_vma = vma;
> +		priv->lock_ctx.locked_vma = vma;
>
>  	return vma;
>  }
> @@ -193,14 +193,14 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
>  static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
>  					 loff_t pos)
>  {

(Also)

We reference priv->lock_ctx 3 times here, either extract as helper var or pass
in direct perhaps?

> -	if (priv->mmap_locked)
> +	if (priv->lock_ctx.mmap_locked)
>  		return false;
>
>  	rcu_read_unlock();
> -	mmap_read_lock(priv->mm);
> +	mmap_read_lock(priv->lock_ctx.mm);
>  	/* Reinitialize the iterator after taking mmap_lock */
>  	vma_iter_set(&priv->iter, pos);
> -	priv->mmap_locked = true;
> +	priv->lock_ctx.mmap_locked = true;
>
>  	return true;
>  }
> @@ -210,12 +210,12 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
>  static inline bool lock_vma_range(struct seq_file *m,
>  				  struct proc_maps_private *priv)
>  {
> -	return mmap_read_lock_killable(priv->mm) == 0;
> +	return mmap_read_lock_killable(priv->lock_ctx.mm) == 0;
>  }
>
>  static inline void unlock_vma_range(struct proc_maps_private *priv)
>  {
> -	mmap_read_unlock(priv->mm);
> +	mmap_read_unlock(priv->lock_ctx.mm);
>  }
>
>  static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> @@ -258,7 +258,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
>  		*ppos = vma->vm_end;
>  	} else {
>  		*ppos = SENTINEL_VMA_GATE;
> -		vma = get_gate_vma(priv->mm);
> +		vma = get_gate_vma(priv->lock_ctx.mm);
>  	}
>
>  	return vma;
> @@ -278,7 +278,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
>  	if (!priv->task)
>  		return ERR_PTR(-ESRCH);
>
> -	mm = priv->mm;
> +	mm = priv->lock_ctx.mm;
>  	if (!mm || !mmget_not_zero(mm)) {
>  		put_task_struct(priv->task);
>  		priv->task = NULL;
> @@ -318,7 +318,7 @@ static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
>  static void m_stop(struct seq_file *m, void *v)
>  {
>  	struct proc_maps_private *priv = m->private;
> -	struct mm_struct *mm = priv->mm;
> +	struct mm_struct *mm = priv->lock_ctx.mm;
>
>  	if (!priv->task)
>  		return;
> @@ -339,9 +339,9 @@ static int proc_maps_open(struct inode *inode, struct file *file,
>  		return -ENOMEM;
>
>  	priv->inode = inode;
> -	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> -	if (IS_ERR_OR_NULL(priv->mm)) {
> -		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> +	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> +	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> +		int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
>
>  		seq_release_private(inode, file);
>  		return err;
> @@ -355,8 +355,8 @@ static int proc_map_release(struct inode *inode, struct file *file)
>  	struct seq_file *seq = file->private_data;
>  	struct proc_maps_private *priv = seq->private;
>
> -	if (priv->mm)
> -		mmdrop(priv->mm);
> +	if (priv->lock_ctx.mm)
> +		mmdrop(priv->lock_ctx.mm);
>
>  	return seq_release_private(inode, file);
>  }
> @@ -610,7 +610,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
>  	if (!!karg.build_id_size != !!karg.build_id_addr)
>  		return -EINVAL;
>
> -	mm = priv->mm;
> +	mm = priv->lock_ctx.mm;
>  	if (!mm || !mmget_not_zero(mm))
>  		return -ESRCH;
>
> @@ -1311,7 +1311,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
>  {
>  	struct proc_maps_private *priv = m->private;
>  	struct mem_size_stats mss = {};
> -	struct mm_struct *mm = priv->mm;
> +	struct mm_struct *mm = priv->lock_ctx.mm;

Nit, but maybe add a

	struct proc_maps_locking_ctx *lock_ctx = priv->lock_ctx;

Here to reduce 'priv->lock_ctx' stuff?

>  	struct vm_area_struct *vma;
>  	unsigned long vma_start = 0, last_vma_end = 0;
>  	int ret = 0;
> @@ -1456,9 +1456,9 @@ static int smaps_rollup_open(struct inode *inode, struct file *file)
>  		goto out_free;
>
>  	priv->inode = inode;
> -	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> -	if (IS_ERR_OR_NULL(priv->mm)) {
> -		ret = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> +	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> +	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> +		ret = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
>
>  		single_release(inode, file);
>  		goto out_free;
> @@ -1476,8 +1476,8 @@ static int smaps_rollup_release(struct inode *inode, struct file *file)
>  	struct seq_file *seq = file->private_data;
>  	struct proc_maps_private *priv = seq->private;
>
> -	if (priv->mm)
> -		mmdrop(priv->mm);
> +	if (priv->lock_ctx.mm)
> +		mmdrop(priv->lock_ctx.mm);
>
>  	kfree(priv);
>  	return single_release(inode, file);
> diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
> index 59bfd61d653a..d362919f4f68 100644
> --- a/fs/proc/task_nommu.c
> +++ b/fs/proc/task_nommu.c
> @@ -204,7 +204,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
>  	if (!priv->task)
>  		return ERR_PTR(-ESRCH);
>
> -	mm = priv->mm;
> +	mm = priv->lock_ctx.mm;
>  	if (!mm || !mmget_not_zero(mm)) {
>  		put_task_struct(priv->task);
>  		priv->task = NULL;
> @@ -226,7 +226,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
>  static void m_stop(struct seq_file *m, void *v)
>  {
>  	struct proc_maps_private *priv = m->private;
> -	struct mm_struct *mm = priv->mm;

(same as above, I reviewed this upsidedown :P)

NIT, but seems sensible to have a

	struct proc_maps_locking_ctx *lock_ctx = priv->lock_ctx;

Here so we can avoid the ugly 'priv->lock_ctx' stuff below.

> +	struct mm_struct *mm = priv->lock_ctx.mm;
>
>  	if (!priv->task)
>  		return;
> @@ -259,9 +259,9 @@ static int maps_open(struct inode *inode, struct file *file,
>  		return -ENOMEM;
>
>  	priv->inode = inode;
> -	priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> -	if (IS_ERR_OR_NULL(priv->mm)) {
> -		int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> +	priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> +	if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> +		int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;

>
>  		seq_release_private(inode, file);
>  		return err;
> @@ -276,8 +276,8 @@ static int map_release(struct inode *inode, struct file *file)
>  	struct seq_file *seq = file->private_data;
>  	struct proc_maps_private *priv = seq->private;
>
> -	if (priv->mm)
> -		mmdrop(priv->mm);
> +	if (priv->lock_ctx.mm)
> +		mmdrop(priv->lock_ctx.mm);
>
>  	return seq_release_private(inode, file);
>  }
> --
> 2.50.1.565.gc32cd1483b-goog
>

On Wed, Aug 6, 2025 at 11:04 AM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> On Wed, Aug 06, 2025 at 08:59:03AM -0700, Suren Baghdasaryan wrote:
> > Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY
> > ioctl are moved into a separate structure. In the next patch this allows
> > ioctl to reuse some of the functions used for reading /proc/pid/maps
> > without using file->private_data. This prevents concurrent modification
> > of file->private_data members by ioctl and /proc/pid/maps readers.
> >
> > The change is pure code refactoring and has no functional changes.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
> > ---
> >  fs/proc/internal.h   | 15 ++++++----
> >  fs/proc/task_mmu.c   | 70 ++++++++++++++++++++++----------------------
> >  fs/proc/task_nommu.c | 14 ++++-----
> >  3 files changed, 52 insertions(+), 47 deletions(-)
> >
> > diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> > index e737401d7383..d1598576506c 100644
> > --- a/fs/proc/internal.h
> > +++ b/fs/proc/internal.h
> > @@ -378,16 +378,21 @@ extern void proc_self_init(void);
> >   * task_[no]mmu.c
> >   */
> >  struct mem_size_stats;
> > -struct proc_maps_private {
> > -     struct inode *inode;
> > -     struct task_struct *task;
> > +
> > +struct proc_maps_locking_ctx {
>
> Decent name :)
>
> >       struct mm_struct *mm;
> > -     struct vma_iterator iter;
> > -     loff_t last_pos;
> >  #ifdef CONFIG_PER_VMA_LOCK
> >       bool mmap_locked;
> >       struct vm_area_struct *locked_vma;
> >  #endif
> > +};
> > +
> > +struct proc_maps_private {
> > +     struct inode *inode;
> > +     struct task_struct *task;
> > +     struct vma_iterator iter;
> > +     loff_t last_pos;
> > +     struct proc_maps_locking_ctx lock_ctx;
> >  #ifdef CONFIG_NUMA
> >       struct mempolicy *task_mempolicy;
> >  #endif
>
> I was going to ask why we have these in internal.h, but then noticed we have to
> have a nommu version of the task_mmu stuff for museum pieces and
> why-do-they-exist arches, sigh.
>
> > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > index ee1e4ccd33bd..45134335e086 100644
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -132,11 +132,11 @@ static void release_task_mempolicy(struct proc_maps_private *priv)
> >
> >  #ifdef CONFIG_PER_VMA_LOCK
> >
> > -static void unlock_vma(struct proc_maps_private *priv)
> > +static void unlock_vma(struct proc_maps_locking_ctx *lock_ctx)
> >  {
> > -     if (priv->locked_vma) {
> > -             vma_end_read(priv->locked_vma);
> > -             priv->locked_vma = NULL;
> > +     if (lock_ctx->locked_vma) {
> > +             vma_end_read(lock_ctx->locked_vma);
> > +             lock_ctx->locked_vma = NULL;
> >       }
> >  }
> >
> > @@ -151,14 +151,14 @@ static inline bool lock_vma_range(struct seq_file *m,
> >        * walking the vma tree under rcu read protection.
> >        */
> >       if (m->op != &proc_pid_maps_op) {
> > -             if (mmap_read_lock_killable(priv->mm))
> > +             if (mmap_read_lock_killable(priv->lock_ctx.mm))
> >                       return false;
> >
> > -             priv->mmap_locked = true;
> > +             priv->lock_ctx.mmap_locked = true;
> >       } else {
> >               rcu_read_lock();
> > -             priv->locked_vma = NULL;
> > -             priv->mmap_locked = false;
> > +             priv->lock_ctx.locked_vma = NULL;
> > +             priv->lock_ctx.mmap_locked = false;
> >       }
> >
> >       return true;
> > @@ -166,10 +166,10 @@ static inline bool lock_vma_range(struct seq_file *m,
> >
> >  static inline void unlock_vma_range(struct proc_maps_private *priv)
> >  {
>
> Not sure why we have unlock_vma() parameterised by proc_maps_locking_ctx but
> this is parameerised by proc_maps_private?
>
> Seems more consistent to have both parameterised by proc_maps_locking_ctx.

True, we can pass just proc_maps_locking_ctx to both lock_vma_range()
and unlock_vma_range(). Will update.

>
> Maybe we'd want lock() forms this way too for consistency?
>
> > -     if (priv->mmap_locked) {
> > -             mmap_read_unlock(priv->mm);
> > +     if (priv->lock_ctx.mmap_locked) {
> > +             mmap_read_unlock(priv->lock_ctx.mm);
> >       } else {
> > -             unlock_vma(priv);
> > +             unlock_vma(&priv->lock_ctx);
> >               rcu_read_unlock();
> >       }
> >  }
> > @@ -179,13 +179,13 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> >  {
> >       struct vm_area_struct *vma;
> >
>
> We reference priv->lock_ctx 3 times here, either extract as helper var or pass
> in direct perhaps?
>
> > -     if (priv->mmap_locked)
> > +     if (priv->lock_ctx.mmap_locked)
> >               return vma_next(&priv->iter);
> >
> > -     unlock_vma(priv);
> > -     vma = lock_next_vma(priv->mm, &priv->iter, last_pos);
> > +     unlock_vma(&priv->lock_ctx);
> > +     vma = lock_next_vma(priv->lock_ctx.mm, &priv->iter, last_pos);
> >       if (!IS_ERR_OR_NULL(vma))
> > -             priv->locked_vma = vma;
> > +             priv->lock_ctx.locked_vma = vma;
> >
> >       return vma;
> >  }
> > @@ -193,14 +193,14 @@ static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> >  static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
> >                                        loff_t pos)
> >  {
>
> (Also)
>
> We reference priv->lock_ctx 3 times here, either extract as helper var or pass
> in direct perhaps?
>
> > -     if (priv->mmap_locked)
> > +     if (priv->lock_ctx.mmap_locked)
> >               return false;
> >
> >       rcu_read_unlock();
> > -     mmap_read_lock(priv->mm);
> > +     mmap_read_lock(priv->lock_ctx.mm);
> >       /* Reinitialize the iterator after taking mmap_lock */
> >       vma_iter_set(&priv->iter, pos);
> > -     priv->mmap_locked = true;
> > +     priv->lock_ctx.mmap_locked = true;
> >
> >       return true;
> >  }
> > @@ -210,12 +210,12 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
> >  static inline bool lock_vma_range(struct seq_file *m,
> >                                 struct proc_maps_private *priv)
> >  {
> > -     return mmap_read_lock_killable(priv->mm) == 0;
> > +     return mmap_read_lock_killable(priv->lock_ctx.mm) == 0;
> >  }
> >
> >  static inline void unlock_vma_range(struct proc_maps_private *priv)
> >  {
> > -     mmap_read_unlock(priv->mm);
> > +     mmap_read_unlock(priv->lock_ctx.mm);
> >  }
> >
> >  static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> > @@ -258,7 +258,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
> >               *ppos = vma->vm_end;
> >       } else {
> >               *ppos = SENTINEL_VMA_GATE;
> > -             vma = get_gate_vma(priv->mm);
> > +             vma = get_gate_vma(priv->lock_ctx.mm);
> >       }
> >
> >       return vma;
> > @@ -278,7 +278,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> >       if (!priv->task)
> >               return ERR_PTR(-ESRCH);
> >
> > -     mm = priv->mm;
> > +     mm = priv->lock_ctx.mm;
> >       if (!mm || !mmget_not_zero(mm)) {
> >               put_task_struct(priv->task);
> >               priv->task = NULL;
> > @@ -318,7 +318,7 @@ static void *m_next(struct seq_file *m, void *v, loff_t *ppos)
> >  static void m_stop(struct seq_file *m, void *v)
> >  {
> >       struct proc_maps_private *priv = m->private;
> > -     struct mm_struct *mm = priv->mm;
> > +     struct mm_struct *mm = priv->lock_ctx.mm;
> >
> >       if (!priv->task)
> >               return;
> > @@ -339,9 +339,9 @@ static int proc_maps_open(struct inode *inode, struct file *file,
> >               return -ENOMEM;
> >
> >       priv->inode = inode;
> > -     priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > -     if (IS_ERR_OR_NULL(priv->mm)) {
> > -             int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> > +     priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > +     if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> > +             int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
> >
> >               seq_release_private(inode, file);
> >               return err;
> > @@ -355,8 +355,8 @@ static int proc_map_release(struct inode *inode, struct file *file)
> >       struct seq_file *seq = file->private_data;
> >       struct proc_maps_private *priv = seq->private;
> >
> > -     if (priv->mm)
> > -             mmdrop(priv->mm);
> > +     if (priv->lock_ctx.mm)
> > +             mmdrop(priv->lock_ctx.mm);
> >
> >       return seq_release_private(inode, file);
> >  }
> > @@ -610,7 +610,7 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
> >       if (!!karg.build_id_size != !!karg.build_id_addr)
> >               return -EINVAL;
> >
> > -     mm = priv->mm;
> > +     mm = priv->lock_ctx.mm;
> >       if (!mm || !mmget_not_zero(mm))
> >               return -ESRCH;
> >
> > @@ -1311,7 +1311,7 @@ static int show_smaps_rollup(struct seq_file *m, void *v)
> >  {
> >       struct proc_maps_private *priv = m->private;
> >       struct mem_size_stats mss = {};
> > -     struct mm_struct *mm = priv->mm;
> > +     struct mm_struct *mm = priv->lock_ctx.mm;
>
> Nit, but maybe add a
>
>         struct proc_maps_locking_ctx *lock_ctx = priv->lock_ctx;
>
> Here to reduce 'priv->lock_ctx' stuff?

Yep, will do that in all the places. Thanks!

>
> >       struct vm_area_struct *vma;
> >       unsigned long vma_start = 0, last_vma_end = 0;
> >       int ret = 0;
> > @@ -1456,9 +1456,9 @@ static int smaps_rollup_open(struct inode *inode, struct file *file)
> >               goto out_free;
> >
> >       priv->inode = inode;
> > -     priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > -     if (IS_ERR_OR_NULL(priv->mm)) {
> > -             ret = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> > +     priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > +     if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> > +             ret = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
> >
> >               single_release(inode, file);
> >               goto out_free;
> > @@ -1476,8 +1476,8 @@ static int smaps_rollup_release(struct inode *inode, struct file *file)
> >       struct seq_file *seq = file->private_data;
> >       struct proc_maps_private *priv = seq->private;
> >
> > -     if (priv->mm)
> > -             mmdrop(priv->mm);
> > +     if (priv->lock_ctx.mm)
> > +             mmdrop(priv->lock_ctx.mm);
> >
> >       kfree(priv);
> >       return single_release(inode, file);
> > diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
> > index 59bfd61d653a..d362919f4f68 100644
> > --- a/fs/proc/task_nommu.c
> > +++ b/fs/proc/task_nommu.c
> > @@ -204,7 +204,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> >       if (!priv->task)
> >               return ERR_PTR(-ESRCH);
> >
> > -     mm = priv->mm;
> > +     mm = priv->lock_ctx.mm;
> >       if (!mm || !mmget_not_zero(mm)) {
> >               put_task_struct(priv->task);
> >               priv->task = NULL;
> > @@ -226,7 +226,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> >  static void m_stop(struct seq_file *m, void *v)
> >  {
> >       struct proc_maps_private *priv = m->private;
> > -     struct mm_struct *mm = priv->mm;
>
> (same as above, I reviewed this upsidedown :P)
>
> NIT, but seems sensible to have a
>
>         struct proc_maps_locking_ctx *lock_ctx = priv->lock_ctx;
>
> Here so we can avoid the ugly 'priv->lock_ctx' stuff below.
>
> > +     struct mm_struct *mm = priv->lock_ctx.mm;
> >
> >       if (!priv->task)
> >               return;
> > @@ -259,9 +259,9 @@ static int maps_open(struct inode *inode, struct file *file,
> >               return -ENOMEM;
> >
> >       priv->inode = inode;
> > -     priv->mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > -     if (IS_ERR_OR_NULL(priv->mm)) {
> > -             int err = priv->mm ? PTR_ERR(priv->mm) : -ESRCH;
> > +     priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> > +     if (IS_ERR_OR_NULL(priv->lock_ctx.mm)) {
> > +             int err = priv->lock_ctx.mm ? PTR_ERR(priv->lock_ctx.mm) : -ESRCH;
>
> >
> >               seq_release_private(inode, file);
> >               return err;
> > @@ -276,8 +276,8 @@ static int map_release(struct inode *inode, struct file *file)
> >       struct seq_file *seq = file->private_data;
> >       struct proc_maps_private *priv = seq->private;
> >
> > -     if (priv->mm)
> > -             mmdrop(priv->mm);
> > +     if (priv->lock_ctx.mm)
> > +             mmdrop(priv->lock_ctx.mm);
> >
> >       return seq_release_private(inode, file);
> >  }
> > --
> > 2.50.1.565.gc32cd1483b-goog
> >

On Wed,  6 Aug 2025 08:59:03 -0700 Suren Baghdasaryan <surenb@google.com> wrote:

> Refactor struct proc_maps_private so that the fields used by PROCMAP_QUERY
> ioctl are moved into a separate structure. In the next patch this allows
> ioctl to reuse some of the functions used for reading /proc/pid/maps
> without using file->private_data. This prevents concurrent modification
> of file->private_data members by ioctl and /proc/pid/maps readers.
> 
> The change is pure code refactoring and has no functional changes.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

[...]