fs: move permission hook out of do_iter_read()

We recently moved fsnotify hook, rw_verify_area() and other checks from
do_iter_write() out to its two callers.

for consistency, do the same thing for do_iter_read() - move the
rw_verify_area() checks and fsnotify hook to the callers vfs_iter_read()
and vfs_readv().

This aligns those vfs helpers with the pattern used in vfs_read() and
vfs_iocb_iter_read() and the vfs write helpers, where all the checks are
in the vfs helpers and the do_* or call_* helpers do the work.

This is needed for fanotify "pre content" events.

Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231122122715.2561213-13-amir73il@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 39 insertions, 27 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index d08d0a3ff7de..9fce8d6968df 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -773,12 +773,14 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
 	return ret;
 }
 
-static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
-		loff_t *pos, rwf_t flags)
+ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
+			   struct iov_iter *iter)
 {
 	size_t tot_len;
 	ssize_t ret = 0;
 
+	if (!file->f_op->read_iter)
+		return -EINVAL;
 	if (!(file->f_mode & FMODE_READ))
 		return -EBADF;
 	if (!(file->f_mode & FMODE_CAN_READ))
@@ -787,22 +789,20 @@ static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
 	tot_len = iov_iter_count(iter);
 	if (!tot_len)
 		goto out;
-	ret = rw_verify_area(READ, file, pos, tot_len);
+	ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
 	if (ret < 0)
 		return ret;
 
-	if (file->f_op->read_iter)
-		ret = do_iter_readv_writev(file, iter, pos, READ, flags);
-	else
-		ret = do_loop_readv_writev(file, iter, pos, READ, flags);
+	ret = call_read_iter(file, iocb, iter);
 out:
 	if (ret >= 0)
 		fsnotify_access(file);
 	return ret;
 }
+EXPORT_SYMBOL(vfs_iocb_iter_read);
 
-ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
-			   struct iov_iter *iter)
+ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
+		      rwf_t flags)
 {
 	size_t tot_len;
 	ssize_t ret = 0;
@@ -817,25 +817,16 @@ ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
 	tot_len = iov_iter_count(iter);
 	if (!tot_len)
 		goto out;
-	ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
+	ret = rw_verify_area(READ, file, ppos, tot_len);
 	if (ret < 0)
 		return ret;
 
-	ret = call_read_iter(file, iocb, iter);
+	ret = do_iter_readv_writev(file, iter, ppos, READ, flags);
 out:
 	if (ret >= 0)
 		fsnotify_access(file);
 	return ret;
 }
-EXPORT_SYMBOL(vfs_iocb_iter_read);
-
-ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
-		rwf_t flags)
-{
-	if (!file->f_op->read_iter)
-		return -EINVAL;
-	return do_iter_read(file, iter, ppos, flags);
-}
 EXPORT_SYMBOL(vfs_iter_read);
 
 ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
@@ -898,19 +889,40 @@ ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
 EXPORT_SYMBOL(vfs_iter_write);
 
 static ssize_t vfs_readv(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_DEST, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
-	if (ret >= 0) {
-		ret = do_iter_read(file, &iter, pos, flags);
-		kfree(iov);
-	}
+	if (!(file->f_mode & FMODE_READ))
+		return -EBADF;
+	if (!(file->f_mode & FMODE_CAN_READ))
+		return -EINVAL;
+
+	ret = import_iovec(ITER_DEST, 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(READ, file, pos, tot_len);
+	if (ret < 0)
+		goto out;
 
+	if (file->f_op->read_iter)
+		ret = do_iter_readv_writev(file, &iter, pos, READ, flags);
+	else
+		ret = do_loop_readv_writev(file, &iter, pos, READ, flags);
+out:
+	if (ret >= 0)
+		fsnotify_access(file);
+	kfree(iov);
 	return ret;
 }