On Fri, Aug 08, 2025 at 08:28:48AM -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@xxxxxxxxxx>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> Acked-by: SeongJae Park <sj@xxxxxxxxxx>
LGTM, so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
> fs/proc/internal.h | 15 +++++---
> fs/proc/task_mmu.c | 87 +++++++++++++++++++++++---------------------
> fs/proc/task_nommu.c | 14 +++----
> 3 files changed, 63 insertions(+), 53 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 29cca0e6d0ff..c0968d293b61 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -132,18 +132,18 @@ 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_ctx_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;
> }
> }
>
> static const struct seq_operations proc_pid_maps_op;
>
> static inline bool lock_vma_range(struct seq_file *m,
> - struct proc_maps_private *priv)
> + struct proc_maps_locking_ctx *lock_ctx)
> {
> /*
> * smaps and numa_maps perform page table walk, therefore require
> @@ -151,25 +151,25 @@ 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(lock_ctx->mm))
> return false;
>
> - priv->mmap_locked = true;
> + lock_ctx->mmap_locked = true;
> } else {
> rcu_read_lock();
> - priv->locked_vma = NULL;
> - priv->mmap_locked = false;
> + lock_ctx->locked_vma = NULL;
> + lock_ctx->mmap_locked = false;
> }
>
> return true;
> }
>
> -static inline void unlock_vma_range(struct proc_maps_private *priv)
> +static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx)
> {
> - if (priv->mmap_locked) {
> - mmap_read_unlock(priv->mm);
> + if (lock_ctx->mmap_locked) {
> + mmap_read_unlock(lock_ctx->mm);
> } else {
> - unlock_vma(priv);
> + unlock_ctx_vma(lock_ctx);
> rcu_read_unlock();
> }
> }
> @@ -177,15 +177,16 @@ static inline void unlock_vma_range(struct proc_maps_private *priv)
> static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> loff_t last_pos)
> {
> + struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx;
> struct vm_area_struct *vma;
>
> - if (priv->mmap_locked)
> + if (lock_ctx->mmap_locked)
> return vma_next(&priv->iter);
>
> - unlock_vma(priv);
> - vma = lock_next_vma(priv->mm, &priv->iter, last_pos);
> + unlock_ctx_vma(lock_ctx);
> + vma = lock_next_vma(lock_ctx->mm, &priv->iter, last_pos);
> if (!IS_ERR_OR_NULL(vma))
> - priv->locked_vma = vma;
> + lock_ctx->locked_vma = vma;
>
> return vma;
> }
> @@ -193,14 +194,16 @@ 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)
> + struct proc_maps_locking_ctx *lock_ctx = &priv->lock_ctx;
> +
> + if (lock_ctx->mmap_locked)
> return false;
>
> rcu_read_unlock();
> - mmap_read_lock(priv->mm);
> + mmap_read_lock(lock_ctx->mm);
> /* Reinitialize the iterator after taking mmap_lock */
> vma_iter_set(&priv->iter, pos);
> - priv->mmap_locked = true;
> + lock_ctx->mmap_locked = true;
>
> return true;
> }
> @@ -208,14 +211,14 @@ static inline bool fallback_to_mmap_lock(struct proc_maps_private *priv,
> #else /* CONFIG_PER_VMA_LOCK */
>
> static inline bool lock_vma_range(struct seq_file *m,
> - struct proc_maps_private *priv)
> + struct proc_maps_locking_ctx *lock_ctx)
> {
> - return mmap_read_lock_killable(priv->mm) == 0;
> + return mmap_read_lock_killable(lock_ctx->mm) == 0;
> }
>
> -static inline void unlock_vma_range(struct proc_maps_private *priv)
> +static inline void unlock_vma_range(struct proc_maps_locking_ctx *lock_ctx)
> {
> - mmap_read_unlock(priv->mm);
> + mmap_read_unlock(lock_ctx->mm);
> }
>
> static struct vm_area_struct *get_next_vma(struct proc_maps_private *priv,
> @@ -258,7 +261,7 @@ 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;
> @@ -267,6 +270,7 @@ static struct vm_area_struct *proc_get_vma(struct seq_file *m, loff_t *ppos)
> static void *m_start(struct seq_file *m, loff_t *ppos)
> {
> struct proc_maps_private *priv = m->private;
> + struct proc_maps_locking_ctx *lock_ctx;
> loff_t last_addr = *ppos;
> struct mm_struct *mm;
>
> @@ -278,14 +282,15 @@ static void *m_start(struct seq_file *m, loff_t *ppos)
> if (!priv->task)
> return ERR_PTR(-ESRCH);
>
> - mm = priv->mm;
> + lock_ctx = &priv->lock_ctx;
> + mm = lock_ctx->mm;
> if (!mm || !mmget_not_zero(mm)) {
> put_task_struct(priv->task);
> priv->task = NULL;
> return NULL;
> }
>
> - if (!lock_vma_range(m, priv)) {
> + if (!lock_vma_range(m, lock_ctx)) {
> mmput(mm);
> put_task_struct(priv->task);
> priv->task = NULL;
> @@ -318,13 +323,13 @@ 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;
>
> release_task_mempolicy(priv);
> - unlock_vma_range(priv);
> + unlock_vma_range(&priv->lock_ctx);
> mmput(mm);
> put_task_struct(priv->task);
> priv->task = NULL;
> @@ -339,9 +344,9 @@ 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(priv->mm)) {
> - int err = PTR_ERR(priv->mm);
> + priv->lock_ctx.mm = proc_mem_open(inode, PTRACE_MODE_READ);
> + if (IS_ERR(priv->lock_ctx.mm)) {
> + int err = PTR_ERR(priv->lock_ctx.mm);
>
> seq_release_private(inode, file);
> return err;
> @@ -355,8 +360,8 @@ 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 +615,7 @@ 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 +1316,7 @@ 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 +1461,9 @@ 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 +1481,8 @@ 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;
We could abstract out lock_ctx here also, but I'm not going to be picky about
it.
>
> 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);
> }
> --
> 2.50.1.703.g449372360f-goog
>
