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([2001:41d0:303:db6b::]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488fb75c695sm22806255e9.14.2026.04.17.11.59.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 11:59:20 -0700 (PDT) From: Tristan Madani X-Google-Original-From: Tristan Madani To: Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+a19ca73b21fe8bc69101@syzkaller.appspotmail.com, stable@vger.kernel.org, Tristan Madani Subject: [PATCH] hfs: return error when bnode already hashed in hfs_bnode_create Date: Fri, 17 Apr 2026 18:59:19 +0000 Message-ID: <20260417185920.182595-1-tristan@talencesecurity.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" hfs_bnode_create() checks if the requested node number is already present in the B-tree hash table. If it is, the function emits a WARN_ON(1) and returns the existing node: if (node) { pr_crit("new node %u already hashed?\n", num); WARN_ON(1); return node; } On crafted HFS images with inconsistent B-tree bitmap data, the allocator can repeatedly request creation of node 0 which is already hashed, triggering this WARNING reliably on every mkdir. Replace the WARN_ON with an error return. The node being already hashed when creation is requested indicates filesystem corruption -- returning ERR_PTR(-EIO) allows the caller to handle this gracefully rather than generating a kernel stack trace. Reported-by: syzbot+a19ca73b21fe8bc69101@syzkaller.appspotmail.com Tested-by: syzbot+a19ca73b21fe8bc69101@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Da19ca73b21fe8bc69101 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Tristan Madani --- fs/hfs/bnode.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c index e8cd1a31f247..69895ccf81ef 100644 --- a/fs/hfs/bnode.c +++ b/fs/hfs/bnode.c @@ -517,8 +517,7 @@ struct hfs_bnode *hfs_bnode_create(struct hfs_btree *tr= ee, u32 num) spin_unlock(&tree->hash_lock); if (node) { pr_crit("new node %u already hashed?\n", num); - WARN_ON(1); - return node; + return ERR_PTR(-EIO); } node =3D __hfs_bnode_create(tree, num); if (!node) --=20 2.47.3