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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>
This commit is contained in:
Paul Aurich
Steve French
parent
7afb867336
commit
a9685b409a
@ -348,6 +348,7 @@ oshr_free:
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SMB2_query_info_free(&rqst[1]);
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free_rsp_buf(resp_buftype[0], rsp_iov[0].iov_base);
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free_rsp_buf(resp_buftype[1], rsp_iov[1].iov_base);
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out:
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if (rc) {
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spin_lock(&cfids->cfid_list_lock);
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if (cfid->on_list) {
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@ -359,23 +360,14 @@ oshr_free:
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/*
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* We are guaranteed to have two references at this
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* point. One for the caller and one for a potential
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* lease. Release the Lease-ref so that the directory
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* will be closed when the caller closes the cached
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* handle.
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* lease. Release one here, and the second below.
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*/
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cfid->has_lease = false;
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spin_unlock(&cfids->cfid_list_lock);
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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goto out;
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}
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spin_unlock(&cfids->cfid_list_lock);
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}
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out:
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if (rc) {
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if (cfid->is_open)
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SMB2_close(0, cfid->tcon, cfid->fid.persistent_fid,
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cfid->fid.volatile_fid);
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free_cached_dir(cfid);
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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} else {
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*ret_cfid = cfid;
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atomic_inc(&tcon->num_remote_opens);
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@ -513,25 +505,24 @@ void invalidate_all_cached_dirs(struct cifs_tcon *tcon)
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cfids->num_entries--;
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cfid->is_open = false;
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cfid->on_list = false;
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/* To prevent race with smb2_cached_lease_break() */
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kref_get(&cfid->refcount);
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if (cfid->has_lease) {
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/*
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* The lease was never cancelled from the server,
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* so steal that reference.
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*/
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cfid->has_lease = false;
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} else
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kref_get(&cfid->refcount);
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}
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spin_unlock(&cfids->cfid_list_lock);
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list_for_each_entry_safe(cfid, q, &entry, entry) {
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list_del(&cfid->entry);
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cancel_work_sync(&cfid->lease_break);
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if (cfid->has_lease) {
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/*
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* We lease was never cancelled from the server so we
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* need to drop the reference.
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*/
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spin_lock(&cfids->cfid_list_lock);
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cfid->has_lease = false;
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spin_unlock(&cfids->cfid_list_lock);
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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}
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/* Drop the extra reference opened above*/
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/*
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* Drop the ref-count from above, either the lease-ref (if there
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* was one) or the extra one acquired.
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*/
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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}
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}
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@ -542,9 +533,6 @@ smb2_cached_lease_break(struct work_struct *work)
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struct cached_fid *cfid = container_of(work,
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struct cached_fid, lease_break);
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spin_lock(&cfid->cfids->cfid_list_lock);
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cfid->has_lease = false;
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spin_unlock(&cfid->cfids->cfid_list_lock);
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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}
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@ -562,6 +550,7 @@ int cached_dir_lease_break(struct cifs_tcon *tcon, __u8 lease_key[16])
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!memcmp(lease_key,
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cfid->fid.lease_key,
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SMB2_LEASE_KEY_SIZE)) {
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cfid->has_lease = false;
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cfid->time = 0;
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/*
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* We found a lease remove it from the list
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@ -639,8 +628,14 @@ static void cfids_laundromat_worker(struct work_struct *work)
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cfid->on_list = false;
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list_move(&cfid->entry, &entry);
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cfids->num_entries--;
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/* To prevent race with smb2_cached_lease_break() */
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kref_get(&cfid->refcount);
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if (cfid->has_lease) {
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/*
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* Our lease has not yet been cancelled from the
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* server. Steal that reference.
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*/
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cfid->has_lease = false;
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} else
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kref_get(&cfid->refcount);
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}
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}
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spin_unlock(&cfids->cfid_list_lock);
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@ -652,17 +647,10 @@ static void cfids_laundromat_worker(struct work_struct *work)
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* with it.
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*/
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cancel_work_sync(&cfid->lease_break);
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if (cfid->has_lease) {
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/*
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* Our lease has not yet been cancelled from the server
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* so we need to drop the reference.
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*/
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spin_lock(&cfids->cfid_list_lock);
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cfid->has_lease = false;
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spin_unlock(&cfids->cfid_list_lock);
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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}
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/* Drop the extra reference opened above */
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/*
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* Drop the ref-count from above, either the lease-ref (if there
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* was one) or the extra one acquired.
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*/
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kref_put(&cfid->refcount, smb2_close_cached_fid);
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}
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queue_delayed_work(cifsiod_wq, &cfids->laundromat_work,
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