CVE-2023-52751

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

smb: client: fix use-after-free in smb2_query_info_compound()

The following UAF was triggered when running fstests generic/072 with

KASAN enabled against Windows Server 2022 and mount options

'multichannel,max_channels=2,vers=3.1.1,mfsymlinks,noperm'

BUG: KASAN: slab-use-after-free in smb2_query_info_compound+0x423/0x6d0 [cifs]

Read of size 8 at addr ffff888014941048 by task xfs_io/27534

CPU: 0 PID: 27534 Comm: xfs_io Not tainted 6.6.0-rc7 #1

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS

rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014

Call Trace:

dump_stack_lvl+0x4a/0x80

print_report+0xcf/0x650

? srso_alias_return_thunk+0x5/0x7f

? srso_alias_return_thunk+0x5/0x7f

? __phys_addr+0x46/0x90

kasan_report+0xda/0x110

? smb2_query_info_compound+0x423/0x6d0 [cifs]

? smb2_query_info_compound+0x423/0x6d0 [cifs]

smb2_query_info_compound+0x423/0x6d0 [cifs]

? __pfx_smb2_query_info_compound+0x10/0x10 [cifs]

? srso_alias_return_thunk+0x5/0x7f

? __stack_depot_save+0x39/0x480

? kasan_save_stack+0x33/0x60

? kasan_set_track+0x25/0x30

? ____kasan_slab_free+0x126/0x170

smb2_queryfs+0xc2/0x2c0 [cifs]

? __pfx_smb2_queryfs+0x10/0x10 [cifs]

? __pfx___lock_acquire+0x10/0x10

smb311_queryfs+0x210/0x220 [cifs]

? __pfx_smb311_queryfs+0x10/0x10 [cifs]

? srso_alias_return_thunk+0x5/0x7f

? __lock_acquire+0x480/0x26c0

? lock_release+0x1ed/0x640

? srso_alias_return_thunk+0x5/0x7f

? do_raw_spin_unlock+0x9b/0x100

cifs_statfs+0x18c/0x4b0 [cifs]

statfs_by_dentry+0x9b/0xf0

fd_statfs+0x4e/0xb0

__do_sys_fstatfs+0x7f/0xe0

? __pfx___do_sys_fstatfs+0x10/0x10

? srso_alias_return_thunk+0x5/0x7f

? lockdep_hardirqs_on_prepare+0x136/0x200

? srso_alias_return_thunk+0x5/0x7f

do_syscall_64+0x3f/0x90

entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Allocated by task 27534:

kasan_save_stack+0x33/0x60

kasan_set_track+0x25/0x30

__kasan_kmalloc+0x8f/0xa0

open_cached_dir+0x71b/0x1240 [cifs]

smb2_query_info_compound+0x5c3/0x6d0 [cifs]

smb2_queryfs+0xc2/0x2c0 [cifs]

smb311_queryfs+0x210/0x220 [cifs]

cifs_statfs+0x18c/0x4b0 [cifs]

statfs_by_dentry+0x9b/0xf0

fd_statfs+0x4e/0xb0

__do_sys_fstatfs+0x7f/0xe0

do_syscall_64+0x3f/0x90

entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Freed by task 27534:

kasan_save_stack+0x33/0x60

kasan_set_track+0x25/0x30

kasan_save_free_info+0x2b/0x50

____kasan_slab_free+0x126/0x170

slab_free_freelist_hook+0xd0/0x1e0

__kmem_cache_free+0x9d/0x1b0

open_cached_dir+0xff5/0x1240 [cifs]

smb2_query_info_compound+0x5c3/0x6d0 [cifs]

smb2_queryfs+0xc2/0x2c0 [cifs]

This is a race between open_cached_dir() and cached_dir_lease_break()

where the cache entry for the open directory handle receives a lease

break while creating it. And before returning from open_cached_dir(),

we put the last reference of the new @cfid because of

!@cfid->has_lease.

Besides the UAF, while running xfstests a lot of missed lease breaks

have been noticed in tests that run several concurrent statfs(2) calls

on those cached fids

CIFS: VFS: \\w22-root1.gandalf.test No task to wake, unknown frame...

CIFS: VFS: \\w22-root1.gandalf.test Cmd: 18 Err: 0x0 Flags: 0x1...

CIFS: VFS: \\w22-root1.gandalf.test smb buf 00000000715bfe83 len 108

CIFS: VFS: Dump pending requests:

CIFS: VFS: \\w22-root1.gandalf.test No task to wake, unknown frame...

CIFS: VFS: \\w22-root1.gandalf.test Cmd: 18 Err: 0x0 Flags: 0x1...

CIFS: VFS: \\w22-root1.gandalf.test smb buf 000000005aa7316e len 108

...

To fix both, in open_cached_dir() ensure that @cfid->has_lease is set

right before sending out compounded request so that any potential

lease break will be get processed by demultiplex thread while we're

still caching @cfid. And, if open failed for some reason, re-check

@cfid->has_lease to decide whether or not put lease reference.