From: Paul Aurich paul@darkrain42.org
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 [ Do not apply the change for cfids_laundromat_worker() since there is no this function and related feature on 6.1.y. Update open_cached_dir() according to method of upstream patch. ] Signed-off-by: Cliff Liu donghua.liu@windriver.com Signed-off-by: He Zhe Zhe.He@windriver.com --- Verified the build test. --- fs/smb/client/cached_dir.c | 39 ++++++++++++++++---------------------- 1 file changed, 16 insertions(+), 23 deletions(-)
diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c index d09226c1ac90..d65d5fe5b8fe 100644 --- a/fs/smb/client/cached_dir.c +++ b/fs/smb/client/cached_dir.c @@ -320,17 +320,13 @@ int open_cached_dir(unsigned int xid, struct cifs_tcon *tcon, /* * We are guaranteed to have two references at this point. * One for the caller and one for a potential lease. - * Release the Lease-ref so that the directory will be closed - * when the caller closes the cached handle. + * Release one here, and the second below. */ kref_put(&cfid->refcount, smb2_close_cached_fid); } if (rc) { - if (cfid->is_open) - SMB2_close(0, cfid->tcon, cfid->fid.persistent_fid, - cfid->fid.volatile_fid); - free_cached_dir(cfid); - cfid = NULL; + cfid->has_lease = false; + kref_put(&cfid->refcount, smb2_close_cached_fid); }
if (rc == 0) { @@ -462,25 +458,24 @@ void invalidate_all_cached_dirs(struct cifs_tcon *tcon) cfids->num_entries--; cfid->is_open = false; cfid->on_list = false; - /* To prevent race with smb2_cached_lease_break() */ - kref_get(&cfid->refcount); + if (cfid->has_lease) { + /* + * The lease was never cancelled from the server, + * so steal that reference. + */ + cfid->has_lease = false; + } else + kref_get(&cfid->refcount); } spin_unlock(&cfids->cfid_list_lock);
list_for_each_entry_safe(cfid, q, &entry, entry) { list_del(&cfid->entry); cancel_work_sync(&cfid->lease_break); - if (cfid->has_lease) { - /* - * We lease was never cancelled from the server so we - * need to drop the reference. - */ - spin_lock(&cfids->cfid_list_lock); - cfid->has_lease = false; - spin_unlock(&cfids->cfid_list_lock); - kref_put(&cfid->refcount, smb2_close_cached_fid); - } - /* Drop the extra reference opened above*/ + /* + * Drop the ref-count from above, either the lease-ref (if there + * was one) or the extra one acquired. + */ kref_put(&cfid->refcount, smb2_close_cached_fid); } } @@ -491,9 +486,6 @@ smb2_cached_lease_break(struct work_struct *work) struct cached_fid *cfid = container_of(work, struct cached_fid, lease_break);
- spin_lock(&cfid->cfids->cfid_list_lock); - cfid->has_lease = false; - spin_unlock(&cfid->cfids->cfid_list_lock); kref_put(&cfid->refcount, smb2_close_cached_fid); }
@@ -511,6 +503,7 @@ int cached_dir_lease_break(struct cifs_tcon *tcon, __u8 lease_key[16]) !memcmp(lease_key, cfid->fid.lease_key, SMB2_LEASE_KEY_SIZE)) { + cfid->has_lease = false; cfid->time = 0; /* * We found a lease remove it from the list