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Subject[PATCH 09/23] fs: add a __kernel_read helper
Date
This is the counterpart to __kernel_write, and skip the rw_verify_area
call compared to kernel_read.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/read_write.c | 23 +++++++++++++++++++++++
include/linux/fs.h | 1 +
2 files changed, 24 insertions(+)

diff --git a/fs/read_write.c b/fs/read_write.c
index bd46c959799e97..cc8e0b4f3cd697 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -430,6 +430,29 @@ ssize_t __vfs_read(struct file *file, char __user *buf, size_t count,
return -EINVAL;
}

+ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
+{
+ mm_segment_t old_fs = get_fs();
+ ssize_t ret;
+
+ if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ)))
+ return -EINVAL;
+ if (!(file->f_mode & FMODE_CAN_READ))
+ return -EINVAL;
+
+ if (count > MAX_RW_COUNT)
+ count = MAX_RW_COUNT;
+ set_fs(KERNEL_DS);
+ ret = __vfs_read(file, (void __user *)buf, count, pos);
+ set_fs(old_fs);
+ if (ret > 0) {
+ fsnotify_access(file);
+ add_rchar(current, ret);
+ }
+ inc_syscr(current);
+ return ret;
+}
+
ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
{
mm_segment_t old_fs;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f881a892ea746..22cbe7b2e91994 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3033,6 +3033,7 @@ extern int kernel_read_file_from_path_initns(const char *, void **, loff_t *, lo
extern int kernel_read_file_from_fd(int, void **, loff_t *, loff_t,
enum kernel_read_file_id);
extern ssize_t kernel_read(struct file *, void *, size_t, loff_t *);
+ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos);
extern ssize_t kernel_write(struct file *, const void *, size_t, loff_t *);
extern ssize_t __kernel_write(struct file *, const void *, size_t, loff_t *);
extern struct file * open_exec(const char *);
--
2.26.2
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