[PATCH 14/16] fs/proc: add proc_mmap_[prepare, complete] hooks for procfs

Lorenzo Stoakes
2025-09-08T11:12:44Z

By adding these hooks we enable procfs implementations to be able to use
the .mmap_prepare, .mmap_complete hooks rather than the deprecated .mmap
hook.

We treat this as if it were any other nested mmap hook and utilise the
.mmap_prepare compatibility layer if necessary.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
fs/proc/inode.c | 13 ++++++++++---
include/linux/proc_fs.h | 5 +++++
2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 129490151be1..d031267e2e4a 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -414,9 +414,16 @@ static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned

static int pde_mmap(struct proc_dir_entry *pde, struct file *file, struct vm_area_struct *vma)
{
- __auto_type mmap = pde->proc_ops->proc_mmap;
- if (mmap)
- return mmap(file, vma);
+ const struct file_operations f_op = {
+ .mmap = pde->proc_ops->proc_mmap,
+ .mmap_prepare = pde->proc_ops->proc_mmap_prepare,
+ .mmap_complete = pde->proc_ops->proc_mmap_complete,
+ };
+
+ if (f_op.mmap)
+ return f_op.mmap(file, vma);
+ else if (f_op.mmap_prepare)
+ return __compat_vma_mmap_prepare(&f_op, file, vma);
return -EIO;
}

diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index f139377f4b31..3573192f813d 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -47,6 +47,11 @@ struct proc_ops {
long (*proc_compat_ioctl)(struct file *, unsigned int, unsigned long);
#endif
int (*proc_mmap)(struct file *, struct vm_area_struct *);
+ int (*proc_mmap_prepare)(struct vm_area_desc *);
+ int (*proc_mmap_complete)(struct file *, struct vm_area_struct *,
+ const void *context);
+ void (*proc_mmap_abort)(const struct file *, const void *vm_private_data,
+ const void *context);
unsigned long (*proc_get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
} __randomize_layout;

--
2.51.0