[PATCH v14 00/23] LSM: Module stacking for AppArmor

Stephen Smalley sds at tycho.nsa.gov
Mon Jan 27 16:14:23 UTC 2020


On 1/24/20 4:49 PM, Casey Schaufler wrote:
> On 1/24/2020 1:04 PM, Stephen Smalley wrote:
>> On 1/23/20 7:22 PM, Casey Schaufler wrote:
>>> This patchset provides the changes required for
>>> the AppArmor security module to stack safely with any other.
>>>
>>> v14: Rebase to 5.5-rc5
>>>        Incorporate feedback from v13
>>>        - Use an array of audit rules (patch 0002)
>>>        - Significant change, removed Acks (patch 0002)
>>>        - Remove unneeded include (patch 0013)
>>>        - Use context.len correctly (patch 0015)
>>>        - Reorder code to be more sensible (patch 0016)
>>>        - Drop SO_PEERCONTEXT as it's not needed yet (patch 0023)
>>
>> I don't know for sure if this is your bug, but it happens every time I boot with your patches applied and not at all on stock v5.5-rc5 so here it is.  Will try to bisect as time permits but not until next week. Trigger seems to be loading the tun driver.
> 
> Thanks. I will have a look as well.

Bisection led to the first patch in the series, "LSM: Infrastructure 
management of the sock security". Still not sure if the bug is in the 
patch itself or just being surfaced by it.

>>
>> [   67.726834] tun: Universal TUN/TAP device driver, 1.6
>> [   67.736657] ==================================================================
>> [   67.741335] BUG: KASAN: slab-out-of-bounds in sock_init_data+0x14a/0x5a0
>> [   67.745037] Read of size 4 at addr ffff88870afe8928 by task libvirtd/1238
>>
>> [   67.751861] CPU: 4 PID: 1238 Comm: libvirtd Tainted: G T 5.5.0-rc5+ #54
>> [   67.756250] Call Trace:
>> [   67.759510]  dump_stack+0xb8/0x110
>> [   67.761604]  print_address_description.constprop.0+0x1f/0x280
>> [   67.763768]  __kasan_report.cold+0x75/0x8f
>> [   67.765895]  ? sock_init_data+0x14a/0x5a0
>> [   67.768282]  kasan_report+0xe/0x20
>> [   67.770397]  sock_init_data+0x14a/0x5a0
>> [   67.772511]  tun_chr_open+0x1de/0x280 [tun]
>> [   67.774644]  misc_open+0x1cb/0x210
>> [   67.776820]  chrdev_open+0x15b/0x350
>> [   67.778917]  ? cdev_put.part.0+0x30/0x30
>> [   67.781030]  do_dentry_open+0x2cb/0x800
>> [   67.783135]  ? cdev_put.part.0+0x30/0x30
>> [   67.785225]  ? devcgroup_check_permission+0x11a/0x260
>> [   67.787321]  ? __x64_sys_fchdir+0xf0/0xf0
>> [   67.789418]  ? security_inode_permission+0x5b/0x70
>> [   67.791513]  path_openat+0x858/0x14a0
>> [   67.793589]  ? path_mountpoint+0x5e0/0x5e0
>> [   67.795719]  ? mark_lock+0xb8/0xb00
>> [   67.797786]  do_filp_open+0x11e/0x1b0
>> [   67.799840]  ? may_open_dev+0x60/0x60
>> [   67.801871]  ? match_held_lock+0x1b/0x240
>> [   67.803968]  ? lock_downgrade+0x360/0x360
>> [   67.805997]  ? do_raw_spin_lock+0x119/0x1d0
>> [   67.808041]  ? rwlock_bug.part.0+0x60/0x60
>> [   67.810099]  ? do_raw_spin_unlock+0xa3/0x130
>> [   67.812244]  ? _raw_spin_unlock+0x1f/0x30
>> [   67.814287]  ? __alloc_fd+0x143/0x2f0
>> [   67.816324]  do_sys_open+0x1f0/0x2d0
>> [   67.818358]  ? filp_open+0x50/0x50
>> [   67.820404]  ? trace_hardirqs_on_thunk+0x1a/0x1c
>> [   67.822447]  ? lockdep_hardirqs_off+0xbe/0x100
>> [   67.824473]  ? mark_held_locks+0x24/0x90
>> [   67.826484]  do_syscall_64+0x74/0xd0
>> [   67.828480]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> [   67.830478] RIP: 0033:0x7f1a2cce6074
>> [   67.832495] Code: 24 20 eb 8f 66 90 44 89 54 24 0c e8 86 f4 ff ff 44 8b 54 24 0c 44 89 e2 48 89 ee 41 89 c0 bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 32 44 89 c7 89 44 24 0c e8 b8 f4 ff ff 8b 44
>> [   67.834760] RSP: 002b:00007f19e4af46d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
>> [   67.837032] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1a2cce6074
>> [   67.839318] RDX: 0000000000000002 RSI: 00007f1a2d0bfb67 RDI: 00000000ffffff9c
>> [   67.841598] RBP: 00007f1a2d0bfb67 R08: 0000000000000000 R09: 00007f19e4af4914
>> [   67.843941] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000002
>> [   67.846283] R13: 000000000000000d R14: 00007f19e4af4920 R15: 00007f1a2d0bfb67
>>
>> [   67.850936] Allocated by task 1238:
>> [   67.853241]  save_stack+0x1b/0x80
>> [   67.855533]  __kasan_kmalloc.constprop.0+0xc2/0xd0
>> [   67.857935]  sk_prot_alloc+0x115/0x170
>> [   67.860235]  sk_alloc+0x2f/0xa10
>> [   67.862541]  tun_chr_open+0x4d/0x280 [tun]
>> [   67.864894]  misc_open+0x1cb/0x210
>> [   67.867164]  chrdev_open+0x15b/0x350
>> [   67.869448]  do_dentry_open+0x2cb/0x800
>> [   67.871768]  path_openat+0x858/0x14a0
>> [   67.874041]  do_filp_open+0x11e/0x1b0
>> [   67.876328]  do_sys_open+0x1f0/0x2d0
>> [   67.878592]  do_syscall_64+0x74/0xd0
>> [   67.880899]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> [   67.885431] Freed by task 726:
>> [   67.887689]  save_stack+0x1b/0x80
>> [   67.889967]  __kasan_slab_free+0x12c/0x170
>> [   67.892197]  kfree+0xff/0x430
>> [   67.894444]  uevent_show+0x176/0x1b0
>> [   67.896709]  dev_attr_show+0x37/0x70
>> [   67.898940]  sysfs_kf_seq_show+0x119/0x210
>> [   67.901159]  seq_read+0x29d/0x720
>> [   67.903367]  vfs_read+0xf9/0x1f0
>> [   67.905538]  ksys_read+0xc9/0x160
>> [   67.907736]  do_syscall_64+0x74/0xd0
>> [   67.909889]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> [   67.914100] The buggy address belongs to the object at ffff88870afe8000
>>                  which belongs to the cache kmalloc-4k of size 4096
>> [   67.918357] The buggy address is located 2344 bytes inside of
>>                  4096-byte region [ffff88870afe8000, ffff88870afe9000)
>> [   67.922562] The buggy address belongs to the page:
>> [   67.924725] page:ffffea001c2bfa00 refcount:1 mapcount:0 mapping:ffff88881f00de00 index:0x0 compound_mapcount: 0
>> [   67.926926] raw: 0017ffe000010200 ffffea001c167a00 0000000200000002 ffff88881f00de00
>> [   67.929144] raw: 0000000000000000 0000000080040004 00000001ffffffff 0000000000000000
>> [   67.931362] page dumped because: kasan: bad access detected
>>
>> [   67.936192] Memory state around the buggy address:
>> [   67.938438]  ffff88870afe8800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>> [   67.941078]  ffff88870afe8880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> [   67.943393] >ffff88870afe8900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> [   67.945709]                                   ^
>> [   67.948000]  ffff88870afe8980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> [   67.950311]  ffff88870afe8a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>> [   67.952629] ==================================================================



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