Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933805AbdLSKPH (ORCPT ); Tue, 19 Dec 2017 05:15:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:35546 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759357AbdLSKPA (ORCPT ); Tue, 19 Dec 2017 05:15:00 -0500 From: Giuseppe Scrivano To: Andrew Morton Cc: LKML , gscrivan@redhat.com, alexander.deucher@amd.com, broonie@kernel.org, chris@chris-wilson.co.uk, David Miller , deepa.kernel@gmail.com, Greg KH , luc.vanoostenryck@gmail.com, lucien xin , Ingo Molnar , Neil Horman , syzkaller-bugs@googlegroups.com, Al Viro , Vladislav Yasevich Subject: [PATCH linux-next] mqueue: fix IPC namespace use-after-free Date: Tue, 19 Dec 2017 11:14:40 +0100 Message-Id: <20171219101440.19736-1-gscrivan@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 19 Dec 2017 10:15:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7203 Lines: 175 mqueue_evict_inode() doesn't access the ipc namespace if it was already freed. It can happen if in a new IPC namespace the inode was created without a prior mq_open() which creates the vfsmount used to access the superblock from mq_clear_sbinfo(). Keep a direct pointer to the superblock used by the inodes so we can correctly reset the reference to the IPC namespace being destroyed. Bug introduced with 9c583773d03633 ("ipc, mqueue: lazy call kern_mount_data in new namespaces") ================================================================== BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline] BUG: KASAN: use-after-free in atomic_read arch/x86/include/asm/atomic.h:27 [inline] BUG: KASAN: use-after-free in refcount_inc_not_zero+0x16e/0x180 lib/refcount.c:120 Read of size 4 at addr ffff8801c51bb200 by task syzkaller711981/3156 CPU: 1 PID: 3156 Comm: syzkaller711981 Not tainted 4.15.0-rc2-mm1+ #39 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 __read_once_size include/linux/compiler.h:183 [inline] atomic_read arch/x86/include/asm/atomic.h:27 [inline] refcount_inc_not_zero+0x16e/0x180 lib/refcount.c:120 refcount_inc+0x15/0x50 lib/refcount.c:153 get_ipc_ns include/linux/ipc_namespace.h:129 [inline] __get_ns_from_inode ipc/mqueue.c:110 [inline] get_ns_from_inode ipc/mqueue.c:118 [inline] mqueue_evict_inode+0x137/0x9c0 ipc/mqueue.c:402 evict+0x481/0x920 fs/inode.c:552 iput_final fs/inode.c:1514 [inline] iput+0x7b9/0xaf0 fs/inode.c:1541 dentry_unlink_inode+0x4b0/0x5e0 fs/dcache.c:376 __dentry_kill+0x3b7/0x6d0 fs/dcache.c:573 shrink_dentry_list+0x3c5/0xcf0 fs/dcache.c:1020 shrink_dcache_parent+0xba/0x230 fs/dcache.c:1454 do_one_tree+0x15/0x50 fs/dcache.c:1485 shrink_dcache_for_umount+0xbb/0x290 fs/dcache.c:1502 generic_shutdown_super+0xcd/0x540 fs/super.c:424 kill_anon_super fs/super.c:987 [inline] kill_litter_super+0x72/0x90 fs/super.c:997 deactivate_locked_super+0x88/0xd0 fs/super.c:312 deactivate_super+0x141/0x1b0 fs/super.c:343 cleanup_mnt+0xb2/0x150 fs/namespace.c:1173 __cleanup_mnt+0x16/0x20 fs/namespace.c:1180 task_work_run+0x199/0x270 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x9bb/0x1ae0 kernel/exit.c:869 do_group_exit+0x149/0x400 kernel/exit.c:972 SYSC_exit_group kernel/exit.c:983 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:981 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x440729 RSP: 002b:00007ffd090ef228 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 0000000000440729 RDX: 0000000000440729 RSI: 0000000000000000 RDI: 0000000000000001 RBP: 00000000006cb018 R08: 0000000000000000 R09: 00000000004002c8 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000401bf0 R13: 0000000000401c80 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 3156: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3614 kmalloc include/linux/slab.h:516 [inline] create_ipc_ns ipc/namespace.c:45 [inline] copy_ipcs+0x1b3/0x520 ipc/namespace.c:96 create_new_namespaces+0x278/0x880 kernel/nsproxy.c:87 unshare_nsproxy_namespaces+0xae/0x1e0 kernel/nsproxy.c:206 SYSC_unshare kernel/fork.c:2421 [inline] SyS_unshare+0x653/0xfa0 kernel/fork.c:2371 entry_SYSCALL_64_fastpath+0x1f/0x96 Freed by task 3156: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3492 [inline] kfree+0xca/0x250 mm/slab.c:3807 free_ipc_ns ipc/namespace.c:139 [inline] put_ipc_ns+0x112/0x150 ipc/namespace.c:164 free_nsproxy+0xc0/0x1f0 kernel/nsproxy.c:180 switch_task_namespaces+0x9d/0xc0 kernel/nsproxy.c:229 exit_task_namespaces+0x17/0x20 kernel/nsproxy.c:234 do_exit+0x9b6/0x1ae0 kernel/exit.c:868 do_group_exit+0x149/0x400 kernel/exit.c:972 SYSC_exit_group kernel/exit.c:983 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:981 entry_SYSCALL_64_fastpath+0x1f/0x96 The buggy address belongs to the object at ffff8801c51bb200 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 0 bytes inside of 2048-byte region [ffff8801c51bb200, ffff8801c51bba00) The buggy address belongs to the page: page:000000007764ba6d count:1 mapcount:0 mapping:000000002c36623f index:0x0 compound_mapcount: 0 flags: 0x2fffc0000008100(slab|head) raw: 02fffc0000008100 ffff8801c51ba100 0000000000000000 0000000100000003 raw: ffffea000715d320 ffff8801dac01950 ffff8801dac00c40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801c51bb100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801c51bb180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff8801c51bb200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801c51bb280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801c51bb300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Reported-by: syzbot Signed-off-by: Giuseppe Scrivano --- include/linux/ipc_namespace.h | 3 ++- ipc/mqueue.c | 6 ++++-- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h index 554e31494f69..29ae2ede7602 100644 --- a/include/linux/ipc_namespace.h +++ b/include/linux/ipc_namespace.h @@ -52,7 +52,8 @@ struct ipc_namespace { struct notifier_block ipcns_nb; /* The kern_mount of the mqueuefs sb. We take a ref on it */ - struct vfsmount *mq_mnt; + struct vfsmount *mq_mnt; + struct super_block *mq_sb; /* # queues in this ns, protected by mq_lock */ unsigned int mq_queues_count; diff --git a/ipc/mqueue.c b/ipc/mqueue.c index 36f177dcb39a..d664c0b0f075 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -341,6 +341,7 @@ static int mqueue_fill_super(struct super_block *sb, void *data, int silent) sb->s_root = d_make_root(inode); if (!sb->s_root) return -ENOMEM; + ns->mq_sb = sb; return 0; } @@ -1554,6 +1555,7 @@ int mq_init_ns(struct ipc_namespace *ns, bool mount) ns->mq_msg_max = DFLT_MSGMAX; ns->mq_msgsize_max = DFLT_MSGSIZEMAX; ns->mq_msg_default = DFLT_MSG; + ns->mq_sb = NULL; ns->mq_msgsize_default = DFLT_MSGSIZE; if (!mount) @@ -1573,8 +1575,8 @@ int mq_init_ns(struct ipc_namespace *ns, bool mount) void mq_clear_sbinfo(struct ipc_namespace *ns) { - if (ns->mq_mnt) - ns->mq_mnt->mnt_sb->s_fs_info = NULL; + if (ns->mq_sb) + ns->mq_sb->s_fs_info = NULL; } void mq_put_mnt(struct ipc_namespace *ns) -- 2.14.3