Re: [syzbot ci] Re: minix: convert to iomap and add direct I/O

[Jeremy Bingham <jbingham@gmail.com>]

#syz test

minix: add the same dentry check as ext4_get_link to minix_get_link

It turns out that minix_get_link does need to have both the sb_bread and
the sb_getblk paths, like ext4_get_link does. It working with just the
sb_bread one initially was deceptive.
---
 fs/minix/namei.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/fs/minix/namei.c b/fs/minix/namei.c
index e245f55a68ff..a4caaa3f7c9a 100644
--- a/fs/minix/namei.c
+++ b/fs/minix/namei.c
@@ -393,12 +393,23 @@ const char *minix_get_link(struct dentry *dentry, struct inode *inode,
 	else
 		blk = v2_block_to_cpu(*(v2_i_data(inode)));
 
-	bh = sb_bread(sb, blk);
-	if (IS_ERR(bh))
-		return ERR_CAST(bh);
-	if (!bh) {
-		pr_err("bad symlink on inode %llu", inode->i_ino);
-		return ERR_PTR(-EFSCORRUPTED);
+	/* This tried dodging the dentry check that ext4 does, but it turns out
+	 * that it's necessary after all.
+	 */
+	if (!dentry) {
+		bh = sb_getblk(sb, blk);
+		if (!bh || !buffer_uptodate(bh)) {
+			brelse(bh);
+			return ERR_PTR(-ECHILD);
+		}
+	} else {
+		bh = sb_bread(sb, blk);
+		if (IS_ERR(bh))
+			return ERR_CAST(bh);
+		if (!bh) {
+			pr_err("bad symlink on inode %llu", inode->i_ino);
+			return ERR_PTR(-EFSCORRUPTED);
+		}
 	}
 
 	set_delayed_call(callback, minix_free_link, bh);
-- 
2.47.3