From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Sat, 3 Oct 2020 02:55:23 +0000 (+0100)
Subject: fs: Allow a NULL pos pointer to __kernel_read
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=7b84b665c874f60d84547635341e418f20cbbab2;p=linux.git

fs: Allow a NULL pos pointer to __kernel_read

Match the behaviour of new_sync_read() and __kernel_write().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/read_write.c b/fs/read_write.c
index 516eb51af70e2..498cc00f3c087 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -449,11 +449,12 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 		return warn_unsupported(file, "read");
 
 	init_sync_kiocb(&kiocb, file);
-	kiocb.ki_pos = *pos;
+	kiocb.ki_pos = pos ? *pos : 0;
 	iov_iter_kvec(&iter, READ, &iov, 1, iov.iov_len);
 	ret = file->f_op->read_iter(&kiocb, &iter);
 	if (ret > 0) {
-		*pos = kiocb.ki_pos;
+		if (pos)
+			*pos = kiocb.ki_pos;
 		fsnotify_access(file);
 		add_rchar(current, ret);
 	}