smb: prevent use-after-free due to open_cached_dir error paths

If open_cached_dir() encounters an error parsing the lease from the
server, the error handling may race with receiving a lease break,
resulting in open_cached_dir() freeing the cfid while the queued work is
pending.

Update open_cached_dir() to drop refs rather than directly freeing the
cfid.

Have cached_dir_lease_break(), cfids_laundromat_worker(), and
invalidate_all_cached_dirs() clear has_lease immediately while still
holding cfids->cfid_list_lock, and then use this to also simplify the
reference counting in cfids_laundromat_worker() and
invalidate_all_cached_dirs().

Fixes this KASAN splat (which manually injects an error and lease break
in open_cached_dir()):

==================================================================
BUG: KASAN: slab-use-after-free in smb2_cached_lease_break+0x27/0xb0
Read of size 8 at addr ffff88811cc24c10 by task kworker/3:1/65

CPU: 3 UID: 0 PID: 65 Comm: kworker/3:1 Not tainted 6.12.0-rc6-g255cf264e6e5-dirty #87
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
Workqueue: cifsiod smb2_cached_lease_break
Call Trace:
 <TASK>
 dump_stack_lvl+0x77/0xb0
 print_report+0xce/0x660
 kasan_report+0xd3/0x110
 smb2_cached_lease_break+0x27/0xb0
 process_one_work+0x50a/0xc50
 worker_thread+0x2ba/0x530
 kthread+0x17c/0x1c0
 ret_from_fork+0x34/0x60
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 2464:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0xaa/0xb0
 open_cached_dir+0xa7d/0x1fb0
 smb2_query_path_info+0x43c/0x6e0
 cifs_get_fattr+0x346/0xf10
 cifs_get_inode_info+0x157/0x210
 cifs_revalidate_dentry_attr+0x2d1/0x460
 cifs_getattr+0x173/0x470
 vfs_statx_path+0x10f/0x160
 vfs_statx+0xe9/0x150
 vfs_fstatat+0x5e/0xc0
 __do_sys_newfstatat+0x91/0xf0
 do_syscall_64+0x95/0x1a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 2464:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3b/0x60
 __kasan_slab_free+0x51/0x70
 kfree+0x174/0x520
 open_cached_dir+0x97f/0x1fb0
 smb2_query_path_info+0x43c/0x6e0
 cifs_get_fattr+0x346/0xf10
 cifs_get_inode_info+0x157/0x210
 cifs_revalidate_dentry_attr+0x2d1/0x460
 cifs_getattr+0x173/0x470
 vfs_statx_path+0x10f/0x160
 vfs_statx+0xe9/0x150
 vfs_fstatat+0x5e/0xc0
 __do_sys_newfstatat+0x91/0xf0
 do_syscall_64+0x95/0x1a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Last potentially related work creation:
 kasan_save_stack+0x33/0x60
 __kasan_record_aux_stack+0xad/0xc0
 insert_work+0x32/0x100
 __queue_work+0x5c9/0x870
 queue_work_on+0x82/0x90
 open_cached_dir+0x1369/0x1fb0
 smb2_query_path_info+0x43c/0x6e0
 cifs_get_fattr+0x346/0xf10
 cifs_get_inode_info+0x157/0x210
 cifs_revalidate_dentry_attr+0x2d1/0x460
 cifs_getattr+0x173/0x470
 vfs_statx_path+0x10f/0x160
 vfs_statx+0xe9/0x150
 vfs_fstatat+0x5e/0xc0
 __do_sys_newfstatat+0x91/0xf0
 do_syscall_64+0x95/0x1a0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff88811cc24c00
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 16 bytes inside of
 freed 1024-byte region [ffff88811cc24c00, ffff88811cc25000)

Cc: stable@vger.kernel.org
Signed-off-by: Paul Aurich <paul@darkrain42.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

0 files changed, 0 insertions, 0 deletions