Description

In the Linux kernel, the following vulnerability has been resolved: hfsplus: fix held lock freed on hfsplus_fill_super() hfsplus_fill_super() calls hfs_find_init() to initialize a search structure, which acquires tree->tree_lock. If the subsequent call to hfsplus_cat_build_key() fails, the function jumps to the out_put_root error label without releasing the lock. The later cleanup path then frees the tree data structure with the lock still held, triggering a held lock freed warning. Fix this by adding the missing hfs_find_exit(&fd) call before jumping to the out_put_root error label. This ensures that tree->tree_lock is properly released on the error path. The bug was originally detected on v6.13-rc1 using an experimental static analysis tool we are developing, and we have verified that the issue persists in the latest mainline kernel. The tool is specifically designed to detect memory management issues. It is currently under active development and not yet publicly available. We confirmed the bug by runtime testing under QEMU with x86_64 defconfig, lockdep enabled, and CONFIG_HFSPLUS_FS=y. To trigger the error path, we used GDB to dynamically shrink the max_unistr_len parameter to 1 before hfsplus_asc2uni() is called. This forces hfsplus_asc2uni() to naturally return -ENAMETOOLONG, which propagates to hfsplus_cat_build_key() and exercises the faulty error path. The following warning was observed during mount: ========================= WARNING: held lock freed! 7.0.0-rc3-00016-gb4f0dd314b39 #4 Not tainted ------------------------- mount/174 is freeing memory ffff888103f92000-ffff888103f92fff, with a lock still held there! ffff888103f920b0 (&tree->tree_lock){+.+.}-{4:4}, at: hfsplus_find_init+0x154/0x1e0 2 locks held by mount/174: #0: ffff888103f960e0 (&type->s_umount_key#42/1){+.+.}-{4:4}, at: alloc_super.constprop.0+0x167/0xa40 #1: ffff888103f920b0 (&tree->tree_lock){+.+.}-{4:4}, at: hfsplus_find_init+0x154/0x1e0 stack backtrace: CPU: 2 UID: 0 PID: 174 Comm: mount Not tainted 7.0.0-rc3-00016-gb4f0dd314b39 #4 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x82/0xd0 debug_check_no_locks_freed+0x13a/0x180 kfree+0x16b/0x510 ? hfsplus_fill_super+0xcb4/0x18a0 hfsplus_fill_super+0xcb4/0x18a0 ? __pfx_hfsplus_fill_super+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? bdev_open+0x65f/0xc30 ? srso_return_thunk+0x5/0x5f ? pointer+0x4ce/0xbf0 ? trace_contention_end+0x11c/0x150 ? __pfx_pointer+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? bdev_open+0x79b/0xc30 ? srso_return_thunk+0x5/0x5f ? srso_return_thunk+0x5/0x5f ? vsnprintf+0x6da/0x1270 ? srso_return_thunk+0x5/0x5f ? __mutex_unlock_slowpath+0x157/0x740 ? __pfx_vsnprintf+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? srso_return_thunk+0x5/0x5f ? mark_held_locks+0x49/0x80 ? srso_return_thunk+0x5/0x5f ? srso_return_thunk+0x5/0x5f ? irqentry_exit+0x17b/0x5e0 ? trace_irq_disable.constprop.0+0x116/0x150 ? __pfx_hfsplus_fill_super+0x10/0x10 ? __pfx_hfsplus_fill_super+0x10/0x10 get_tree_bdev_flags+0x302/0x580 ? __pfx_get_tree_bdev_flags+0x10/0x10 ? vfs_parse_fs_qstr+0x129/0x1a0 ? __pfx_vfs_parse_fs_qstr+0x3/0x10 vfs_get_tree+0x89/0x320 fc_mount+0x10/0x1d0 path_mount+0x5c5/0x21c0 ? __pfx_path_mount+0x10/0x10 ? trace_irq_enable.constprop.0+0x116/0x150 ? trace_irq_enable.constprop.0+0x116/0x150 ? srso_return_thunk+0x5/0x5f ? srso_return_thunk+0x5/0x5f ? kmem_cache_free+0x307/0x540 ? user_path_at+0x51/0x60 ? __x64_sys_mount+0x212/0x280 ? srso_return_thunk+0x5/0x5f __x64_sys_mount+0x212/0x280 ? __pfx___x64_sys_mount+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? trace_irq_enable.constprop.0+0x116/0x150 ? srso_return_thunk+0x5/0x5f do_syscall_64+0x111/0x680 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7ffacad55eae Code: 48 8b 0d 85 1f 0f 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 8 RSP: 002b ---truncated---

References 8

• git.kernel.org https://git.kernel.org/stable/c/041acda6d9f96006703466449c10c9a69590c8b9
• git.kernel.org https://git.kernel.org/stable/c/3ca80e3012c8be85b4f8d0d20eac8d3b17ff257e
• git.kernel.org https://git.kernel.org/stable/c/6499c9c8ec437a369e7e221dad91f6122b50759d
• git.kernel.org https://git.kernel.org/stable/c/90c500e4fd83fa33c09bc7ee23b6d9cc487ac733
• git.kernel.org https://git.kernel.org/stable/c/bfbcce6a7b0552a390620d9b2c4d2bcb1825cbdc
• git.kernel.org https://git.kernel.org/stable/c/c554ddc87af4d4e4be42f8aed1baec9e1c7588e0
• git.kernel.org https://git.kernel.org/stable/c/d309d3308de658d87c42d97e044c89a226327526
• git.kernel.org https://git.kernel.org/stable/c/e890656accee4c26d932ea388eb8936a6e22184d

Remediation