The patch titled Subject: hfs: fix missing hfs_bnode_get() in __hfs_bnode_create has been added to the -mm mm-nonmm-unstable branch. Its filename is hfs-fix-missing-hfs_bnode_get-in-__hfs_bnode_create.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-nonmm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Liu Shixin liushixin2@huawei.com Subject: hfs: fix missing hfs_bnode_get() in __hfs_bnode_create Date: Mon, 12 Dec 2022 10:16:27 +0800

Syzbot found a kernel BUG in hfs_bnode_put():

kernel BUG at fs/hfs/bnode.c:466! invalid opcode: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 3634 Comm: kworker/u4:5 Not tainted 6.1.0-rc7-syzkaller-00190-g97ee9d1c1696 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Workqueue: writeback wb_workfn (flush-7:0) RIP: 0010:hfs_bnode_put+0x46f/0x480 fs/hfs/bnode.c:466 Code: 8a 80 ff e9 73 fe ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c a0 fe ff ff 48 89 df e8 db 8a 80 ff e9 93 fe ff ff e8 a1 68 2c ff <0f> 0b e8 9a 68 2c ff 0f 0b 0f 1f 84 00 00 00 00 00 55 41 57 41 56 RSP: 0018:ffffc90003b4f258 EFLAGS: 00010293 RAX: ffffffff825e318f RBX: 0000000000000000 RCX: ffff8880739dd7c0 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc90003b4f430 R08: ffffffff825e2d9b R09: ffffed10045157d1 R10: ffffed10045157d1 R11: 1ffff110045157d0 R12: ffff8880228abe80 R13: ffff88807016c000 R14: dffffc0000000000 R15: ffff8880228abe00 FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa6ebe88718 CR3: 000000001e93d000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> hfs_write_inode+0x1bc/0xb40 write_inode fs/fs-writeback.c:1440 [inline] __writeback_single_inode+0x4d6/0x670 fs/fs-writeback.c:1652 writeback_sb_inodes+0xb3b/0x18f0 fs/fs-writeback.c:1878 __writeback_inodes_wb+0x125/0x420 fs/fs-writeback.c:1949 wb_writeback+0x440/0x7b0 fs/fs-writeback.c:2054 wb_check_start_all fs/fs-writeback.c:2176 [inline] wb_do_writeback fs/fs-writeback.c:2202 [inline] wb_workfn+0x827/0xef0 fs/fs-writeback.c:2235 process_one_work+0x877/0xdb0 kernel/workqueue.c:2289 worker_thread+0xb14/0x1330 kernel/workqueue.c:2436 kthread+0x266/0x300 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 </TASK>

The BUG_ON() is triggered at here:

/* Dispose of resources used by a node */ void hfs_bnode_put(struct hfs_bnode *node) { if (node) { <skipped> BUG_ON(!atomic_read(&node->refcnt)); <- we have issue here!!!! <skipped> } }

By tracing the refcnt, I found the node is created by hfs_bmap_alloc() with refcnt 1. Then the node is used by hfs_btree_write(). There is a missing of hfs_bnode_get() after find the node. The issue happened in following path:

<alloc> hfs_bmap_alloc hfs_bnode_find __hfs_bnode_create <- allocate a new node with refcnt 1. hfs_bnode_put <- decrease the refcnt

<write> hfs_btree_write hfs_bnode_find __hfs_bnode_create hfs_bnode_findhash <- find the node without refcnt increased. hfs_bnode_put <- trigger the BUG_ON() since refcnt is 0.

Link: https://lkml.kernel.org/r/20221212021627.3766829-1-liushixin2@huawei.com Reported-by: syzbot+5b04b49a7ec7226c7426@syzkaller.appspotmail.com Signed-off-by: Liu Shixin liushixin2@huawei.com Cc: Fabio M. De Francesco fmdefrancesco@gmail.com Cc: Viacheslav Dubeyko slava@dubeyko.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/hfs/bnode.c | 1 + 1 file changed, 1 insertion(+)

--- a/fs/hfs/bnode.c~hfs-fix-missing-hfs_bnode_get-in-__hfs_bnode_create +++ a/fs/hfs/bnode.c @@ -274,6 +274,7 @@ static struct hfs_bnode *__hfs_bnode_cre tree->node_hash[hash] = node; tree->node_hash_cnt++; } else { + hfs_bnode_get(node2); spin_unlock(&tree->hash_lock); kfree(node); wait_event(node2->lock_wq, !test_bit(HFS_BNODE_NEW, &node2->flags)); _

Patches currently in -mm which might be from liushixin2@huawei.com are

hfs-fix-missing-hfs_bnode_get-in-__hfs_bnode_create.patch