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.
Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Check if @cfid->time is set in laundromat so we guarantee that only
fully cached fids will be selected for removal. While we're at it,
add missing locks to protect access of @cfid fields in order to avoid
races with open_cached_dir() and cfids_laundromat_worker(),
respectively.
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
By having laundromat kthread processing cached directories on every
second turned out to be overkill, especially when having multiple SMB
mounts.
Relax it by using a delayed worker instead that gets scheduled on
every @dir_cache_timeout (default=30) seconds per tcon.
This also fixes the 1s delay when tearing down tcon.
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
disabled
When no directory lease support, or for IPC shares where directories
can not be opened, do not start an unneeded laundromat thread for
that mount (it wastes resources).
Fixes: d14de8067e ("cifs: Add a laundromat thread for cached directories")
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Acked-by: Tom Talpey <tom@talpey.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Allow adjusting the maximum number of cached directories per share
(defaults to 16) via mount parm "max_cached_dirs"
Signed-off-by: Steve French <stfrench@microsoft.com>
Currently with directory leases we cache directory contents for a fixed period
of time (default 30 seconds) but for many workloads this is too short. Allow
configuring the maximum amount of time directory entries are cached when a
directory lease is held on that directory. Add module load parm "max_dir_cache"
For example to set the timeout to 10 minutes you would do:
echo 600 > /sys/module/cifs/parameters/dir_cache_timeout
or to disable caching directory contents:
echo 0 > /sys/module/cifs/parameters/dir_cache_timeout
Reviewed-by: Bharath SM <bharathsm@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
We read and cache directory contents when we get directory
lease, so we should ask for read permission to read contents
of directory.
Signed-off-by: Bharath SM <bharathsm@microsoft.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Move CIFS/SMB3 related client and server files (cifs.ko and ksmbd.ko
and helper modules) to new fs/smb subdirectory:
fs/cifs --> fs/smb/client
fs/ksmbd --> fs/smb/server
fs/smbfs_common --> fs/smb/common
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
