diff mbox series

[10/15] fs: move permission hook out of do_iter_write()

Message ID 20231114153321.1716028-11-amir73il@gmail.com (mailing list archive)
State New, archived
Headers show
Series Tidy up file permission hooks | expand

Commit Message

Amir Goldstein Nov. 14, 2023, 3:33 p.m. UTC 
In many of the vfs helpers, the rw_verity_area() checks are called before
taking sb_start_write(), making them "start-write-safe".
do_iter_write() is an exception to this rule.

do_iter_write() has two callers - vfs_iter_write() and vfs_writev().
Move rw_verify_area() and other checks from do_iter_write() out to
its callers to make them "start-write-safe".

Move also the fsnotify_modify() hook to align with similar pattern
used in vfs_write() and other vfs helpers.

This is needed for fanotify "pre content" events.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/read_write.c | 76 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 46 insertions(+), 30 deletions(-)

Comments

Christian Brauner Nov. 21, 2023, 3:34 p.m. UTC | #1 
On Tue, Nov 14, 2023 at 05:33:16PM +0200, Amir Goldstein wrote:
> In many of the vfs helpers, the rw_verity_area() checks are called before
> taking sb_start_write(), making them "start-write-safe".
> do_iter_write() is an exception to this rule.
> 
> do_iter_write() has two callers - vfs_iter_write() and vfs_writev().
> Move rw_verify_area() and other checks from do_iter_write() out to
> its callers to make them "start-write-safe".
> 
> Move also the fsnotify_modify() hook to align with similar pattern
> used in vfs_write() and other vfs helpers.
> 
> This is needed for fanotify "pre content" events.
> 
> Suggested-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  fs/read_write.c | 76 ++++++++++++++++++++++++++++++-------------------
>  1 file changed, 46 insertions(+), 30 deletions(-)
> 
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 8cdc6e6a9639..d4891346d42e 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -848,28 +848,10 @@ EXPORT_SYMBOL(vfs_iter_read);
>  static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
>  			     loff_t *pos, rwf_t flags)
>  {
> -	size_t tot_len;
> -	ssize_t ret = 0;
> -
> -	if (!(file->f_mode & FMODE_WRITE))
> -		return -EBADF;
> -	if (!(file->f_mode & FMODE_CAN_WRITE))
> -		return -EINVAL;
> -
> -	tot_len = iov_iter_count(iter);
> -	if (!tot_len)
> -		return 0;
> -	ret = rw_verify_area(WRITE, file, pos, tot_len);
> -	if (ret < 0)
> -		return ret;
> -
>  	if (file->f_op->write_iter)
> -		ret = do_iter_readv_writev(file, iter, pos, WRITE, flags);
> +		return do_iter_readv_writev(file, iter, pos, WRITE, flags);
>  	else
> -		ret = do_loop_readv_writev(file, iter, pos, WRITE, flags);
> -	if (ret > 0)
> -		fsnotify_modify(file);
> -	return ret;
> +		return do_loop_readv_writev(file, iter, pos, WRITE, flags);

Nit, this will end up being:

static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
                             loff_t *pos, rwf_t flags)
{
        if (file->f_op->write_iter)
                return do_iter_readv_writev(file, iter, pos, WRITE, flags);
        else
                return do_loop_readv_writev(file, iter, pos, WRITE, flags);
}

which is probably best written as:

static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
                             loff_t *pos, rwf_t flags)
{
        if (file->f_op->write_iter)
                return do_iter_readv_writev(file, iter, pos, WRITE, flags);

        return do_loop_readv_writev(file, iter, pos, WRITE, flags);
}
diff mbox series

Patch

diff --git a/fs/read_write.c b/fs/read_write.c
index 8cdc6e6a9639..d4891346d42e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -848,28 +848,10 @@  EXPORT_SYMBOL(vfs_iter_read);
 static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
 			     loff_t *pos, rwf_t flags)
 {
-	size_t tot_len;
-	ssize_t ret = 0;
-
-	if (!(file->f_mode & FMODE_WRITE))
-		return -EBADF;
-	if (!(file->f_mode & FMODE_CAN_WRITE))
-		return -EINVAL;
-
-	tot_len = iov_iter_count(iter);
-	if (!tot_len)
-		return 0;
-	ret = rw_verify_area(WRITE, file, pos, tot_len);
-	if (ret < 0)
-		return ret;
-
 	if (file->f_op->write_iter)
-		ret = do_iter_readv_writev(file, iter, pos, WRITE, flags);
+		return do_iter_readv_writev(file, iter, pos, WRITE, flags);
 	else
-		ret = do_loop_readv_writev(file, iter, pos, WRITE, flags);
-	if (ret > 0)
-		fsnotify_modify(file);
-	return ret;
+		return do_loop_readv_writev(file, iter, pos, WRITE, flags);
 }
 
 ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
@@ -903,13 +885,28 @@  EXPORT_SYMBOL(vfs_iocb_iter_write);
 ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
 		       rwf_t flags)
 {
-	int ret;
+	size_t tot_len;
+	ssize_t ret;
 
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_WRITE))
+		return -EINVAL;
 	if (!file->f_op->write_iter)
 		return -EINVAL;
 
+	tot_len = iov_iter_count(iter);
+	if (!tot_len)
+		return 0;
+
+	ret = rw_verify_area(WRITE, file, ppos, tot_len);
+	if (ret < 0)
+		return ret;
+
 	file_start_write(file);
 	ret = do_iter_write(file, iter, ppos, flags);
+	if (ret > 0)
+		fsnotify_modify(file);
 	file_end_write(file);
 
 	return ret;
@@ -934,20 +931,39 @@  static ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
 }
 
 static ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
-		   unsigned long vlen, loff_t *pos, rwf_t flags)
+			  unsigned long vlen, loff_t *pos, rwf_t flags)
 {
 	struct iovec iovstack[UIO_FASTIOV];
 	struct iovec *iov = iovstack;
 	struct iov_iter iter;
-	ssize_t ret;
+	size_t tot_len;
+	ssize_t ret = 0;
 
-	ret = import_iovec(ITER_SOURCE, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
-	if (ret >= 0) {
-		file_start_write(file);
-		ret = do_iter_write(file, &iter, pos, flags);
-		file_end_write(file);
-		kfree(iov);
-	}
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_WRITE))
+		return -EINVAL;
+
+	ret = import_iovec(ITER_SOURCE, vec, vlen, ARRAY_SIZE(iovstack), &iov,
+			   &iter);
+	if (ret < 0)
+		return ret;
+
+	tot_len = iov_iter_count(&iter);
+	if (!tot_len)
+		goto out;
+
+	ret = rw_verify_area(WRITE, file, pos, tot_len);
+	if (ret < 0)
+		goto out;
+
+	file_start_write(file);
+	ret = do_iter_write(file, &iter, pos, flags);
+	if (ret > 0)
+		fsnotify_modify(file);
+	file_end_write(file);
+out:
+	kfree(iov);
 	return ret;
 }