From d8a73cc46c8462a969a7516131feb3096f4c49d3 Mon Sep 17 00:00:00 2001 From: Shardul Bankar Date: Tue, 30 Dec 2025 02:19:38 +0530 Subject: [PATCH] hfsplus: return error when node already exists in hfs_bnode_create When hfs_bnode_create() finds that a node is already hashed (which should not happen in normal operation), it currently returns the existing node without incrementing its reference count. This causes a reference count inconsistency that leads to a kernel panic when the node is later freed in hfs_bnode_put(): kernel BUG at fs/hfsplus/bnode.c:676! BUG_ON(!atomic_read(&node->refcnt)) This scenario can occur when hfs_bmap_alloc() attempts to allocate a node that is already in use (e.g., when node 0's bitmap bit is incorrectly unset), or due to filesystem corruption. Returning an existing node from a create path is not normal operation. Fix this by returning ERR_PTR(-EEXIST) instead of the node when it's already hashed. This properly signals the error condition to callers, which already check for IS_ERR() return values. Reported-by: syzbot+1c8ff72d0cd8a50dfeaa@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?extid=1c8ff72d0cd8a50dfeaa Link: https://lore.kernel.org/all/784415834694f39902088fa8946850fc1779a318.camel@ibm.com/ Fixes: 634725a92938 ("[PATCH] hfs: cleanup HFS+ prints") Signed-off-by: Shardul Bankar Reviewed-by: Viacheslav Dubeyko Signed-off-by: Viacheslav Dubeyko Link: https://lore.kernel.org/r/20251229204938.1907089-1-shardul.b@mpiricsoftware.com Signed-off-by: Viacheslav Dubeyko --- fs/hfsplus/bnode.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c index 191661af96778..250a226336ea7 100644 --- a/fs/hfsplus/bnode.c +++ b/fs/hfsplus/bnode.c @@ -629,7 +629,7 @@ struct hfs_bnode *hfs_bnode_create(struct hfs_btree *tree, u32 num) if (node) { pr_crit("new node %u already hashed?\n", num); WARN_ON(1); - return node; + return ERR_PTR(-EEXIST); } node = __hfs_bnode_create(tree, num); if (!node) -- 2.47.3