smb: Don't leak cfid when reconnect races with open_cached_dir
CVE: CVE-2024-53178
Component: kernel
CWE: CWE-401
Severity: Moderate
CVSS v3: 6.3/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H
Release date: 2024-12-27T00:00:00+00:00

In the Linux kernel, the following vulnerability has been resolved:

smb: Don't leak cfid when reconnect races with open_cached_dir

open_cached_dir() may either race with the tcon reconnection even before
compound_send_recv() or directly trigger a reconnection via
SMB2_open_init() or SMB_query_info_init().

The reconnection process invokes invalidate_all_cached_dirs() via
cifs_mark_open_files_invalid(), which removes all cfids from the
cfids->entries list but doesn't drop a ref if has_lease isn't true. This
results in the currently-being-constructed cfid not being on the list,
but still having a refcount of 2. It leaks if returned from
open_cached_dir().

Fix this by setting cfid->has_lease when the ref is actually taken; the
cfid will not be used by other threads until it has a valid time.

Addresses these kmemleaks:

unreferenced object 0xffff8881090c4000 (size 1024):
  comm "bash", pid 1860, jiffies 4295126592
  hex dump (first 32 bytes):
    00 01 00 00 00 00 ad de 22 01 00 00 00 00 ad de  ........".......
    00 ca 45 22 81 88 ff ff f8 dc 4f 04 81 88 ff ff  ..E"......O.....
  backtrace (crc 6f58c20f):
    [<ffffffff8b895a1e>] __kmalloc_cache_noprof+0x2be/0x350
    [<ffffffff8bda06e3>] open_cached_dir+0x993/0x1fb0
    [<ffffffff8bdaa750>] cifs_readdir+0x15a0/0x1d50
    [<ffffffff8b9a853f>] iterate_dir+0x28f/0x4b0
    [<ffffffff8b9a9aed>] __x64_sys_getdents64+0xfd/0x200
    [<ffffffff8cf6da05>] do_syscall_64+0x95/0x1a0
    [<ffffffff8d00012f>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
unreferenced object 0xffff8881044fdcf8 (size 8):
  comm "bash", pid 1860, jiffies 4295126592
  hex dump (first 8 bytes):
    00 cc cc cc cc cc cc cc                          ........
  backtrace (crc 10c106a9):
    [<ffffffff8b89a3d3>] __kmalloc_node_track_caller_noprof+0x363/0x480
    [<ffffffff8b7d7256>] kstrdup+0x36/0x60
    [<ffffffff8bda0700>] open_cached_dir+0x9b0/0x1fb0
    [<ffffffff8bdaa750>] cifs_readdir+0x15a0/0x1d50
    [<ffffffff8b9a853f>] iterate_dir+0x28f/0x4b0
    [<ffffffff8b9a9aed>] __x64_sys_getdents64+0xfd/0x200
    [<ffffffff8cf6da05>] do_syscall_64+0x95/0x1a0
    [<ffffffff8d00012f>] entry_SYSCALL_64_after_hwframe+0x76/0x7e

And addresses these BUG splats when unmounting the SMB filesystem:

BUG: Dentry ffff888140590ba0{i=1000000000080,n=/}  still in use (2) [unmount of cifs cifs]
WARNING: CPU: 3 PID: 3433 at fs/dcache.c:1536 umount_check+0xd0/0x100
Modules linked in:
CPU: 3 UID: 0 PID: 3433 Comm: bash Not tainted 6.12.0-rc4-g850925a8133c-dirty #49
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
RIP: 0010:umount_check+0xd0/0x100
Code: 8d 7c 24 40 e8 31 5a f4 ff 49 8b 54 24 40 41 56 49 89 e9 45 89 e8 48 89 d9 41 57 48 89 de 48 c7 c7 80 e7 db ac e8 f0 72 9a ff <0f> 0b 58 31 c0 5a 5b 5d 41 5c 41 5d 41 5e 41 5f e9 2b e5 5d 01 41
RSP: 0018:ffff88811cc27978 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff888140590ba0 RCX: ffffffffaaf20bae
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: ffff8881f6fb6f40
RBP: ffff8881462ec000 R08: 0000000000000001 R09: ffffed1023984ee3
R10: ffff88811cc2771f R11: 00000000016cfcc0 R12: ffff888134383e08
R13: 0000000000000002 R14: ffff8881462ec668 R15: ffffffffaceab4c0
FS:  00007f23bfa98740(0000) GS:ffff8881f6f80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000556de4a6f808 CR3: 0000000123c80000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 d_walk+0x6a/0x530
 shrink_dcache_for_umount+0x6a/0x200
 generic_shutdown_super+0x52/0x2a0
 kill_anon_super+0x22/0x40
 cifs_kill_sb+0x159/0x1e0
 deactivate_locked_super+0x66/0xe0
 cleanup_mnt+0x140/0x210
 task_work_run+0xfb/0x170
 syscall_exit_to_user_mode+0x29f/0x2b0
 do_syscall_64+0xa1/0x1a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f23bfb93ae7
Code: ff ff ff ff c3 66 0f 1f 44 00 00 48 8b 0d 11 93 0d 00 f7 d8 64 89 01 b8 ff ff ff ff eb bf 0f 1f 44 00 00 b8 50 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e9 92 0d 00 f7 d8 64 89 
---truncated---


Remediation: