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fs: factor out backing_file_mmap() helper

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Assert that the file object is allocated in a backing_file container
so that file_user_path() could be used to display the user path and
not the backing file's path in /proc/<pid>/maps.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
This commit is contained in:
Amir Goldstein 2023-10-13 12:49:37 +03:00
parent 9b7e9e2f5d
commit f567377e40
3 changed files with 35 additions and 17 deletions
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27
fs/backing-file.c
View File

@ -11,6 +11,7 @@
#include <linux/fs.h>
#include <linux/backing-file.h>
#include <linux/splice.h>
#include <linux/mm.h>
#include "internal.h"
@ -296,6 +297,32 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
}
EXPORT_SYMBOL_GPL(backing_file_splice_write);
int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
struct backing_file_ctx *ctx)
{
const struct cred *old_cred;
int ret;
if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)) ||
WARN_ON_ONCE(ctx->user_file != vma->vm_file))
return -EIO;
if (!file->f_op->mmap)
return -ENODEV;
vma_set_file(vma, file);
old_cred = override_creds(ctx->cred);
ret = call_mmap(vma->vm_file, vma);
revert_creds(old_cred);
if (ctx->accessed)
ctx->accessed(ctx->user_file);
return ret;
}
EXPORT_SYMBOL_GPL(backing_file_mmap);
static int __init backing_aio_init(void)
{
backing_aio_cachep = kmem_cache_create("backing_aio",

23
fs/overlayfs/file.c
View File

@ -10,7 +10,6 @@
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <linux/security.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/backing-file.h>
#include "overlayfs.h"
@ -415,23 +414,13 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
{
struct file *realfile = file->private_data;
const struct cred *old_cred;
int ret;
struct backing_file_ctx ctx = {
.cred = ovl_creds(file_inode(file)->i_sb),
.user_file = file,
.accessed = ovl_file_accessed,
};
if (!realfile->f_op->mmap)
return -ENODEV;
if (WARN_ON(file != vma->vm_file))
return -EIO;
vma_set_file(vma, realfile);
old_cred = ovl_override_creds(file_inode(file)->i_sb);
ret = call_mmap(vma->vm_file, vma);
revert_creds(old_cred);
ovl_file_accessed(file);
return ret;
return backing_file_mmap(realfile, vma, &ctx);
}
static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)

2
include/linux/backing-file.h
View File

@ -36,5 +36,7 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
struct file *out, loff_t *ppos, size_t len,
unsigned int flags,
struct backing_file_ctx *ctx);
int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
struct backing_file_ctx *ctx);
#endif /* _LINUX_BACKING_FILE_H */