linux-kernel - Re: [syzbot] [PATCH] Re: [syzbot] [jfs?] KASAN: null-ptr-deref Read in drop

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Message-ID: <6807ec80.050a0220.36a438.0001.GAE@google.com>
Date: Tue, 22 Apr 2025 12:22:40 -0700
From: syzbot <syzbot+de1498ff3a934ac5e8b4@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] [PATCH] Re: [syzbot] [jfs?] KASAN: null-ptr-deref Read
 in drop_buffers (3)

For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org.

***

Subject: [PATCH] Re: [syzbot] [jfs?] KASAN: null-ptr-deref Read in drop_buffers (3)
Author: richard120310@...il.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git cb82ca153949

Signed-off-by: I Hsin Cheng <richard120310@...il.com>
---
 fs/buffer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/buffer.c b/fs/buffer.c
index cc8452f60251..e65a754176c1 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2883,6 +2883,8 @@ drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
 	struct buffer_head *head = folio_buffers(folio);
 	struct buffer_head *bh;
 
+	if (!head)
+		goto out;
 	bh = head;
 	do {
 		if (buffer_busy(bh))
@@ -2897,6 +2899,7 @@ drop_buffers(struct folio *folio, struct buffer_head **buffers_to_free)
 			__remove_assoc_queue(bh);
 		bh = next;
 	} while (bh != head);
+out:
 	*buffers_to_free = head;
 	folio_detach_private(folio);
 	return true;
-- 
2.43.0