CVE-2023-53862 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
hfs: fix missing hfs_bnode_get() in __hfs_bnode_create
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.
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Analysis
by VulDB Data Team • 03/30/2026
The vulnerability CVE-2023-53862 represents a critical kernel memory management flaw within the Linux HFS (Hierarchical File System) implementation that manifests as an invalid opcode panic during kernel execution. This issue resides in the hfs_bnode_put() function at fs/hfs/bnode.c line 466, where a BUG_ON() macro triggers due to an unexpected reference count value of zero. The root cause stems from an improper reference counting mechanism during node allocation and retrieval operations, specifically within the hfs_bnode_find() function where hfs_bnode_get() is omitted after node lookup, leading to a premature decrement of the reference counter. This vulnerability directly maps to CWE-691, which addresses insufficient control of a resource through reuse, and aligns with ATT&CK technique T1068, involving privilege escalation through kernel exploitation. The flaw occurs during file system write operations when the kernel attempts to manage b-tree node references, creating a scenario where a node can be marked as freed while still being referenced, ultimately causing a kernel panic and system instability.
The technical implementation of this vulnerability involves a complex interplay between memory allocation, reference counting, and concurrent access patterns within the HFS file system driver. When hfs_bmap_alloc() allocates a new bnode, it correctly initializes the reference count to one through __hfs_bnode_create(), but during subsequent write operations via hfs_btree_write(), the hfs_bnode_find() function fails to increment the reference count before returning the node. This omission creates a race condition where the node reference count drops to zero, triggering the BUG_ON() macro in hfs_bnode_put() and causing an immediate kernel crash. The system call trace reveals the execution path through the writeback subsystem, where kworker threads attempt to flush dirty inodes, ultimately leading to the problematic node management sequence. The kernel's KASAN (Kernel Address Sanitizer) detection confirms the invalid memory access pattern, indicating that the reference count validation fails because the node was improperly released from the hash table without proper reference incrementation. This pattern of missing reference counting operations creates a persistent vulnerability that can be exploited to cause system crashes or potentially more severe privilege escalation attacks.
The operational impact of CVE-2023-53862 extends beyond simple system instability, as it represents a fundamental flaw in the Linux kernel's file system management capabilities that could be leveraged by malicious actors to create denial-of-service conditions or potentially exploit kernel memory corruption patterns. The vulnerability affects systems running Linux kernel versions that include the HFS file system implementation, particularly those utilizing HFS+ volumes, which are common in Apple operating systems and cross-platform environments. Attackers could potentially trigger this vulnerability through sustained write operations on HFS+ volumes, causing system crashes and disrupting normal file system operations. The implications for system reliability are significant, as this flaw could be exploited in environments where continuous file system access is required, such as servers, embedded systems, or virtualized environments where HFS+ file systems are in use. The vulnerability's classification as a kernel panic condition means that successful exploitation could result in complete system shutdown, requiring manual intervention and potentially leading to data loss if systems are not properly backed up.
Mitigation strategies for CVE-2023-53862 should focus on immediate kernel updates from the Linux kernel maintainers, as the fix involves correcting the reference counting logic in the hfs_bnode_find() function to properly increment reference counts after node lookup operations. System administrators should prioritize patching affected kernel versions and monitoring for potential exploitation attempts through kernel log analysis for instances of BUG_ON() triggers or memory management errors. The fix requires ensuring that hfs_bnode_get() is called immediately after hfs_bnode_find() to properly increment the reference count before the node is used, preventing the premature decrement that leads to the kernel panic. Additional monitoring should be implemented to detect unusual file system write patterns that might trigger the vulnerability, particularly in environments with high I/O workloads on HFS+ volumes. Organizations should also consider implementing automated patch management systems to ensure timely deployment of kernel updates and should conduct regular security assessments to identify other potential reference counting vulnerabilities within the kernel's file system subsystems. The vulnerability highlights the importance of rigorous kernel code review processes for memory management operations and proper reference counting implementation in multi-threaded kernel environments.