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@xxxxxxxxxx>
> Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> 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
>
