| From: Vincent Whitchurch <vincent.whitchurch@axis.com> |
| Date: Thu, 23 Jan 2020 17:09:06 +0100 |
| Subject: CIFS: Fix task struct use-after-free on reconnect |
| |
| commit f1f27ad74557e39f67a8331a808b860f89254f2d upstream. |
| |
| The task which created the MID may be gone by the time cifsd attempts to |
| call the callbacks on MIDs from cifs_reconnect(). |
| |
| This leads to a use-after-free of the task struct in cifs_wake_up_task: |
| |
| ================================================================== |
| BUG: KASAN: use-after-free in __lock_acquire+0x31a0/0x3270 |
| Read of size 8 at addr ffff8880103e3a68 by task cifsd/630 |
| |
| CPU: 0 PID: 630 Comm: cifsd Not tainted 5.5.0-rc6+ #119 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 |
| Call Trace: |
| dump_stack+0x8e/0xcb |
| print_address_description.constprop.5+0x1d3/0x3c0 |
| ? __lock_acquire+0x31a0/0x3270 |
| __kasan_report+0x152/0x1aa |
| ? __lock_acquire+0x31a0/0x3270 |
| ? __lock_acquire+0x31a0/0x3270 |
| kasan_report+0xe/0x20 |
| __lock_acquire+0x31a0/0x3270 |
| ? __wake_up_common+0x1dc/0x630 |
| ? _raw_spin_unlock_irqrestore+0x4c/0x60 |
| ? mark_held_locks+0xf0/0xf0 |
| ? _raw_spin_unlock_irqrestore+0x39/0x60 |
| ? __wake_up_common_lock+0xd5/0x130 |
| ? __wake_up_common+0x630/0x630 |
| lock_acquire+0x13f/0x330 |
| ? try_to_wake_up+0xa3/0x19e0 |
| _raw_spin_lock_irqsave+0x38/0x50 |
| ? try_to_wake_up+0xa3/0x19e0 |
| try_to_wake_up+0xa3/0x19e0 |
| ? cifs_compound_callback+0x178/0x210 |
| ? set_cpus_allowed_ptr+0x10/0x10 |
| cifs_reconnect+0xa1c/0x15d0 |
| ? generic_ip_connect+0x1860/0x1860 |
| ? rwlock_bug.part.0+0x90/0x90 |
| cifs_readv_from_socket+0x479/0x690 |
| cifs_read_from_socket+0x9d/0xe0 |
| ? cifs_readv_from_socket+0x690/0x690 |
| ? mempool_resize+0x690/0x690 |
| ? rwlock_bug.part.0+0x90/0x90 |
| ? memset+0x1f/0x40 |
| ? allocate_buffers+0xff/0x340 |
| cifs_demultiplex_thread+0x388/0x2a50 |
| ? cifs_handle_standard+0x610/0x610 |
| ? rcu_read_lock_held_common+0x120/0x120 |
| ? mark_lock+0x11b/0xc00 |
| ? __lock_acquire+0x14ed/0x3270 |
| ? __kthread_parkme+0x78/0x100 |
| ? lockdep_hardirqs_on+0x3e8/0x560 |
| ? lock_downgrade+0x6a0/0x6a0 |
| ? lockdep_hardirqs_on+0x3e8/0x560 |
| ? _raw_spin_unlock_irqrestore+0x39/0x60 |
| ? cifs_handle_standard+0x610/0x610 |
| kthread+0x2bb/0x3a0 |
| ? kthread_create_worker_on_cpu+0xc0/0xc0 |
| ret_from_fork+0x3a/0x50 |
| |
| Allocated by task 649: |
| save_stack+0x19/0x70 |
| __kasan_kmalloc.constprop.5+0xa6/0xf0 |
| kmem_cache_alloc+0x107/0x320 |
| copy_process+0x17bc/0x5370 |
| _do_fork+0x103/0xbf0 |
| __x64_sys_clone+0x168/0x1e0 |
| do_syscall_64+0x9b/0xec0 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| Freed by task 0: |
| save_stack+0x19/0x70 |
| __kasan_slab_free+0x11d/0x160 |
| kmem_cache_free+0xb5/0x3d0 |
| rcu_core+0x52f/0x1230 |
| __do_softirq+0x24d/0x962 |
| |
| The buggy address belongs to the object at ffff8880103e32c0 |
| which belongs to the cache task_struct of size 6016 |
| The buggy address is located 1960 bytes inside of |
| 6016-byte region [ffff8880103e32c0, ffff8880103e4a40) |
| The buggy address belongs to the page: |
| page:ffffea000040f800 refcount:1 mapcount:0 mapping:ffff8880108da5c0 |
| index:0xffff8880103e4c00 compound_mapcount: 0 |
| raw: 4000000000010200 ffffea00001f2208 ffffea00001e3408 ffff8880108da5c0 |
| raw: ffff8880103e4c00 0000000000050003 00000001ffffffff 0000000000000000 |
| page dumped because: kasan: bad access detected |
| |
| Memory state around the buggy address: |
| ffff8880103e3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ffff8880103e3980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| >ffff8880103e3a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ^ |
| ffff8880103e3a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ffff8880103e3b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb |
| ================================================================== |
| |
| This can be reliably reproduced by adding the below delay to |
| cifs_reconnect(), running find(1) on the mount, restarting the samba |
| server while find is running, and killing find during the delay: |
| |
| spin_unlock(&GlobalMid_Lock); |
| mutex_unlock(&server->srv_mutex); |
| |
| + msleep(10000); |
| + |
| cifs_dbg(FYI, "%s: issuing mid callbacks\n", __func__); |
| list_for_each_safe(tmp, tmp2, &retry_list) { |
| mid_entry = list_entry(tmp, struct mid_q_entry, qhead); |
| |
| Fix this by holding a reference to the task struct until the MID is |
| freed. |
| |
| Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> |
| Signed-off-by: Steve French <stfrench@microsoft.com> |
| Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz> |
| Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com> |
| [bwh: Backported to 3.16: |
| - In _cifs_mid_q_entry_release(), use mid instead of midEntry |
| - Adjust context, indentation] |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| --- a/fs/cifs/cifsglob.h |
| +++ b/fs/cifs/cifsglob.h |
| @@ -1252,6 +1252,7 @@ struct mid_q_entry { |
| mid_receive_t *receive; /* call receive callback */ |
| mid_callback_t *callback; /* call completion callback */ |
| void *callback_data; /* general purpose pointer for callback */ |
| + struct task_struct *creator; |
| void *resp_buf; /* pointer to received SMB header */ |
| int mid_state; /* wish this were enum but can not pass to wait_event */ |
| unsigned int mid_flags; |
| --- a/fs/cifs/smb2transport.c |
| +++ b/fs/cifs/smb2transport.c |
| @@ -542,6 +542,8 @@ smb2_mid_entry_alloc(const struct smb2_h |
| * The default is for the mid to be synchronous, so the |
| * default callback just wakes up the current task. |
| */ |
| + get_task_struct(current); |
| + temp->creator = current; |
| temp->callback = cifs_wake_up_task; |
| temp->callback_data = current; |
| } |
| --- a/fs/cifs/transport.c |
| +++ b/fs/cifs/transport.c |
| @@ -72,6 +72,8 @@ AllocMidQEntry(const struct smb_hdr *smb |
| * The default is for the mid to be synchronous, so the |
| * default callback just wakes up the current task. |
| */ |
| + get_task_struct(current); |
| + temp->creator = current; |
| temp->callback = cifs_wake_up_task; |
| temp->callback_data = current; |
| } |
| @@ -86,6 +88,8 @@ static void _cifs_mid_q_entry_release(st |
| struct mid_q_entry *mid = container_of(refcount, struct mid_q_entry, |
| refcount); |
| |
| + put_task_struct(mid->creator); |
| + |
| mempool_free(mid, cifs_mid_poolp); |
| } |
| |
