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Yang Chenzhi 5882e7c8cd hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create 
[ Upstream commit 152af11428 ]

When sync() and link() are called concurrently, both threads may
enter hfs_bnode_find() without finding the node in the hash table
and proceed to create it.

Thread A:
  hfsplus_write_inode()
    -> hfsplus_write_system_inode()
      -> hfs_btree_write()
        -> hfs_bnode_find(tree, 0)
          -> __hfs_bnode_create(tree, 0)

Thread B:
  hfsplus_create_cat()
    -> hfs_brec_insert()
      -> hfs_bnode_split()
        -> hfs_bmap_alloc()
          -> hfs_bnode_find(tree, 0)
            -> __hfs_bnode_create(tree, 0)

In this case, thread A creates the bnode, sets refcnt=1, and hashes it.
Thread B also tries to create the same bnode, notices it has already
been inserted, drops its own instance, and uses the hashed one without
getting the node.

```

	node2 = hfs_bnode_findhash(tree, cnid);
	if (!node2) {                                 <- Thread A
		hash = hfs_bnode_hash(cnid);
		node->next_hash = tree->node_hash[hash];
		tree->node_hash[hash] = node;
		tree->node_hash_cnt++;
	} else {                                      <- Thread B
		spin_unlock(&tree->hash_lock);
		kfree(node);
		wait_event(node2->lock_wq,
			!test_bit(HFS_BNODE_NEW, &node2->flags));
		return node2;
	}
```

However, hfs_bnode_find() requires each call to take a reference.
Here both threads end up setting refcnt=1. When they later put the node,
this triggers:

BUG_ON(!atomic_read(&node->refcnt))

In this scenario, Thread B in fact finds the node in the hash table
rather than creating a new one, and thus must take a reference.

Fix this by calling hfs_bnode_get() when reusing a bnode newly created by
another thread to ensure the refcount is updated correctly.

A similar bug was fixed in HFS long ago in commit
a9dc087fd3 ("fix missing hfs_bnode_get() in __hfs_bnode_create")
but the same issue remained in HFS+ until now.

Reported-by: syzbot+005d2a9ecd9fbf525f6a@syzkaller.appspotmail.com
Signed-off-by: Yang Chenzhi <yang.chenzhi@vivo.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/20250829093912.611853-1-yang.chenzhi@vivo.com
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-01-02 12:56:40 +01:00
arch x86/microcode: Mark early_parse_cmdline() as __init 2026-01-02 12:56:39 +01:00
block block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list_lock 2025-12-18 14:03:40 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: ahash - Zero positive err value in ahash_update_finish 2025-12-18 14:03:12 +01:00
Documentation docs: hwmon: fix link to g762 devicetree binding 2025-12-18 14:03:38 +01:00
drivers crypto: ccp - Add support for PCI device 0x115A 2026-01-02 12:56:40 +01:00
fs hfsplus: fix missing hfs_bnode_get() in __hfs_bnode_create 2026-01-02 12:56:40 +01:00
include shmem: fix recovery on rename failures 2026-01-02 12:56:37 +01:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/kbuf: use READ_ONCE() for userspace-mapped memory 2025-12-18 14:03:36 +01:00
ipc namespace-6.18-rc1 2025-09-29 11:20:29 -07:00
kernel livepatch: Match old_sympos 0 and 1 in klp_find_func() 2026-01-02 12:56:39 +01:00
lib lib/vsprintf: Check pointer before dereferencing in time_and_date() 2025-12-18 14:02:58 +01:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm shmem: fix recovery on rename failures 2026-01-02 12:56:37 +01:00
net net/sched: sch_cake: Fix incorrect qlen reduction in cake_drop 2025-12-18 14:03:31 +01:00
rust rust: Add -fno-isolate-erroneous-paths-dereference to bindgen_skip_c_flags 2025-11-10 08:37:06 +08:00
samples samples: work around glibc redefining some of our defines wrong 2025-11-21 09:29:02 -08:00
scripts kbuild: Use objtree for module signing key path 2026-01-02 12:56:40 +01:00
security landlock: Fix handling of disconnected directories 2025-12-18 14:03:27 +01:00
sound ALSA: wavefront: Fix integer overflow in sample size validation 2025-12-18 14:03:43 +01:00
tools perf stat: Allow no events to open if this is a "--null" run 2025-12-18 14:03:32 +01:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying 2025-11-04 09:16:53 -08:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.2 2025-12-18 14:03:43 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.