linux-kernel - [PATCH v2] bcachefs: fix null-ptr-deref in have

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Message-Id: <20241025115618.2908-1-aha310510@gmail.com>
Date: Fri, 25 Oct 2024 20:56:18 +0900
From: Jeongjun Park <aha310510@...il.com>
To: kent.overstreet@...ux.dev
Cc: linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syzbot+b468b9fef56949c3b528@...kaller.appspotmail.com,
	Jeongjun Park <aha310510@...il.com>
Subject: [PATCH v2] bcachefs: fix null-ptr-deref in have_stripes()

c->btree_roots_known[i].b can be NULL. In this case, a NULL pointer dereference
occurs, so you need to add code to check the variable.

Reported-by: syzbot+b468b9fef56949c3b528@...kaller.appspotmail.com
Fixes: 7773df19c35f ("bcachefs: metadata version bucket_stripe_sectors")
Signed-off-by: Jeongjun Park <aha310510@...il.com>
---
 fs/bcachefs/sb-downgrade.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
index ae715ff658e8..8767c33c2b51 100644
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -143,6 +143,9 @@ UPGRADE_TABLE()
 
 static int have_stripes(struct bch_fs *c)
 {
+	if (IS_ERR_OR_NULL(c->btree_roots_known[BTREE_ID_stripes].b))
+		return 0;
+
 	return !btree_node_fake(c->btree_roots_known[BTREE_ID_stripes].b);
 }
 
--