On Wed, Jan 9, 2019 at 11:11 AM Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > On Wed, 2019-01-09 at 07:41 -0800, syzbot wrote: > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: a88cc8da0279 Merge branch 'akpm' (patches from > > Andrew) > > git tree: upstream > > console output: > > https://syzkaller.appspot.com/x/log.txt?x=1722da4f400000 > > kernel config: > > https://syzkaller.appspot.com/x/.config?x=edf1c3031097c304 > > dashboard link: > > https://syzkaller.appspot.com/bug?extid=6664500f0f18f07a5c0e > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: > > https://syzkaller.appspot.com/x/repro.syz?x=12d43580c00000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the > > commit: > > Reported-by: syzbot+6664500f0f18f07a5c0e@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > SELinux: failed to load policy > > sel_write_load: 238 callbacks suppressed > > SELinux: failed to load policy > > kasan: CONFIG_KASAN_INLINE enabled > > kasan: GPF could be caused by NULL-ptr deref or user memory access > > general protection fault: 0000 [#1] PREEMPT SMP KASAN > > CPU: 0 PID: 9316 Comm: syz-executor2 Not tainted 5.0.0-rc1+ #16 > > Hardware name: Google Google Compute Engine/Google Compute Engine, > > BIOS > > Google 01/01/2011 > > RIP: 0010:ebitmap_destroy+0x32/0xf0 security/selinux/ss/ebitmap.c:334 > > Code: 49 89 fd 41 54 53 e8 9d e6 36 fe 4d 85 ed 0f 84 99 00 00 00 e8 > > 8f e6 > > 36 fe 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 > > 00 0f > > 85 98 00 00 00 49 be 00 00 00 00 00 fc ff df 4d 8b > > RSP: 0018:ffff88808967f5c0 EFLAGS: 00010202 > > RAX: dffffc0000000000 RBX: ffff88808967f6a8 RCX: dffffc0000000000 > > RDX: 0000000000000001 RSI: ffffffff834b1081 RDI: 0000000000000008 > > RBP: ffff88808967f5e0 R08: ffff8880972a8140 R09: ffffed1015cc5b90 > > R10: ffffed1015cc5b8f R11: ffff8880ae62dc7b R12: ffff888099d993c0 > > R13: 0000000000000008 R14: ffff888099d993c0 R15: ffff88808967f648 > > FS: 00007f70cd9e5700(0000) GS:ffff8880ae600000(0000) > > knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 00000000015e7938 CR3: 0000000096c4a000 CR4: 00000000001406f0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > sens_destroy+0x49/0xa0 security/selinux/ss/policydb.c:735 > > sens_read+0x25d/0x460 security/selinux/ss/policydb.c:1636 > > policydb_read+0xed9/0x60d0 security/selinux/ss/policydb.c:2430 > > security_load_policy+0x423/0x1830 > > security/selinux/ss/services.c:2129 > > sel_write_load+0x25a/0x470 security/selinux/selinuxfs.c:565 > > __vfs_write+0x116/0xb40 fs/read_write.c:485 > > vfs_write+0x20c/0x580 fs/read_write.c:549 > > ksys_write+0x105/0x260 fs/read_write.c:598 > > __do_sys_write fs/read_write.c:610 [inline] > > __se_sys_write fs/read_write.c:607 [inline] > > __x64_sys_write+0x73/0xb0 fs/read_write.c:607 > > do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x457ec9 > > Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 > > 89 f7 > > 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 > > f0 ff > > ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007f70cd9e4c78 EFLAGS: 00000246 ORIG_RAX: > > 0000000000000001 > > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457ec9 > > RDX: 000000000000005c RSI: 0000000020000000 RDI: 0000000000000003 > > RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f70cd9e56d4 > > R13: 00000000004c720f R14: 00000000004dc9a0 R15: 00000000ffffffff > > Modules linked in: > > ---[ end trace 78ea480790940b53 ]--- > > RIP: 0010:ebitmap_destroy+0x32/0xf0 security/selinux/ss/ebitmap.c:334 > > Code: 49 89 fd 41 54 53 e8 9d e6 36 fe 4d 85 ed 0f 84 99 00 00 00 e8 > > 8f e6 > > 36 fe 4c 89 ea 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 > > 00 0f > > 85 98 00 00 00 49 be 00 00 00 00 00 fc ff df 4d 8b > > RSP: 0018:ffff88808967f5c0 EFLAGS: 00010202 > > RAX: dffffc0000000000 RBX: ffff88808967f6a8 RCX: dffffc0000000000 > > RDX: 0000000000000001 RSI: ffffffff834b1081 RDI: 0000000000000008 > > RBP: ffff88808967f5e0 R08: ffff8880972a8140 R09: ffffed1015cc5b90 > > R10: ffffed1015cc5b8f R11: ffff8880ae62dc7b R12: ffff888099d993c0 > > R13: 0000000000000008 R14: ffff888099d993c0 R15: ffff88808967f648 > > FS: 00007f70cd9e5700(0000) GS:ffff8880ae700000(0000) > > knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 000000000073c000 CR3: 0000000096c4a000 CR4: 00000000001406e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Possible fix below > > From cc9324299f32db326447a28a836c462fc16bc945 Mon Sep 17 00:00:00 2001 > From: Stephen Smalley <sds@xxxxxxxxxxxxx> > Date: Wed, 9 Jan 2019 10:55:10 -0500 > Subject: [PATCH] selinux: fix GPF on invalid policy > > levdatum->level can be NULL if we encounter an error while loading > the policy during sens_read prior to initializing it. Make sure > sens_destroy handles that case correctly. > > Reported-by: syzbot+6664500f0f18f07a5c0e@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx> > --- > security/selinux/ss/policydb.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c > index a50d625e7946..c1c31e33657a 100644 > --- a/security/selinux/ss/policydb.c > +++ b/security/selinux/ss/policydb.c > @@ -732,7 +732,8 @@ static int sens_destroy(void *key, void *datum, void *p) > kfree(key); > if (datum) { > levdatum = datum; > - ebitmap_destroy(&levdatum->level->cat); > + if (levdatum->level) > + ebitmap_destroy(&levdatum->level->cat); > kfree(levdatum->level); > } > kfree(datum); > -- > 2.20.1 ... > > syzbot can test patches for this bug, for details see: > > https://goo.gl/tpsmEJ#testing-patches I'm not sure if this particular bug is one that syzbot can reproduce (I recall a different message when it had a reproducer), but it would be nice to get some syzbot test verification if possible when posting (see the link above for the magic). Regardless, this looks like a good fix to me; I'm going to merge it into the stable-5.0 tree and assuming all goes well I'll probably send it up to Linus early next week. -- paul moore www.paul-moore.com
