CVE-2023-52572

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

cifs: Fix UAF in cifs_demultiplex_thread()

There is a UAF when xfstests on cifs:

BUG: KASAN: use-after-free in smb2_is_network_name_deleted+0x27/0x160

Read of size 4 at addr ffff88810103fc08 by task cifsd/923

CPU: 1 PID: 923 Comm: cifsd Not tainted 6.1.0-rc4+ #45

...

Call Trace:

<TASK>

dump_stack_lvl+0x34/0x44

print_report+0x171/0x472

kasan_report+0xad/0x130

kasan_check_range+0x145/0x1a0

smb2_is_network_name_deleted+0x27/0x160

cifs_demultiplex_thread.cold+0x172/0x5a4

kthread+0x165/0x1a0

ret_from_fork+0x1f/0x30

</TASK>

Allocated by task 923:

kasan_save_stack+0x1e/0x40

kasan_set_track+0x21/0x30

__kasan_slab_alloc+0x54/0x60

kmem_cache_alloc+0x147/0x320

mempool_alloc+0xe1/0x260

cifs_small_buf_get+0x24/0x60

allocate_buffers+0xa1/0x1c0

cifs_demultiplex_thread+0x199/0x10d0

kthread+0x165/0x1a0

ret_from_fork+0x1f/0x30

Freed by task 921:

kasan_save_stack+0x1e/0x40

kasan_set_track+0x21/0x30

kasan_save_free_info+0x2a/0x40

____kasan_slab_free+0x143/0x1b0

kmem_cache_free+0xe3/0x4d0

cifs_small_buf_release+0x29/0x90

SMB2_negotiate+0x8b7/0x1c60

smb2_negotiate+0x51/0x70

cifs_negotiate_protocol+0xf0/0x160

cifs_get_smb_ses+0x5fa/0x13c0

mount_get_conns+0x7a/0x750

cifs_mount+0x103/0xd00

cifs_smb3_do_mount+0x1dd/0xcb0

smb3_get_tree+0x1d5/0x300

vfs_get_tree+0x41/0xf0

path_mount+0x9b3/0xdd0

__x64_sys_mount+0x190/0x1d0

do_syscall_64+0x35/0x80

entry_SYSCALL_64_after_hwframe+0x46/0xb0

The UAF is because:

mount(pid: 921) | cifsd(pid: 923)

-------------------------------|-------------------------------

| cifs_demultiplex_thread

SMB2_negotiate |

cifs_send_recv |

compound_send_recv |

smb_send_rqst |

wait_for_response |

wait_event_state [1] |

| standard_receive3

| cifs_handle_standard

| handle_mid

| mid->resp_buf = buf; [2]

| dequeue_mid [3]

KILL the process [4] |

resp_iov[i].iov_base = buf |

free_rsp_buf [5] |

| is_network_name_deleted [6]

| callback

1. After send request to server, wait the response until

mid->mid_state != SUBMITTED;

2. Receive response from server, and set it to mid;

3. Set the mid state to RECEIVED;

4. Kill the process, the mid state already RECEIVED, get 0;

5. Handle and release the negotiate response;

6. UAF.

It can be easily reproduce with add some delay in [3] - [6].

Only sync call has the problem since async call's callback is

executed in cifsd process.

Add an extra state to mark the mid state to READY before wakeup the

waitter, then it can get the resp safely.