Re: kernel BUG at drivers/android/binder_alloc.c:LINE! (3)

[Todd Kjos <tkjos@google.com>]

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The fix for this is in Greg KH's char-misc-linus branch. Pointing
syzbot at it to verify:

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
char-misc-linus


On Thu, Mar 28, 2019 at 9:14 AM syzbot
<syzbot+f9f3f388440283da2965@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    1a9df9e2 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11fed11f200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8dcdce25ea72bedf
> dashboard link: https://syzkaller.appspot.com/bug?extid=f9f3f388440283da2965
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17d05637200000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1677e62f200000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+f9f3f388440283da2965@syzkaller.appspotmail.com
>
> binder: 7824:7824 DecRefs 0 refcount change on invalid ref 1 ret -22
> ------------[ cut here ]------------
> kernel BUG at drivers/android/binder_alloc.c:1141!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 7824 Comm: syz-executor570 Not tainted 5.1.0-rc2+ #40
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:binder_alloc_do_buffer_copy+0xd6/0x510
> drivers/android/binder_alloc.c:1141
> Code: 02 00 0f 85 20 04 00 00 4d 8b 64 24 58 49 29 dc e8 4f f4 23 fc 4c 89
> e6 4c 89 ef e8 64 f5 23 fc 4d 39 e5 76 07 e8 3a f4 23 fc <0f> 0b e8 33 f4
> 23 fc 4c 8b 75 d0 4d 29 ec 4c 89 e6 4c 89 f7 e8 41
> RSP: 0018:ffff88808b497550 EFLAGS: 00010293
> RAX: ffff88808620e540 RBX: 0000000020001000 RCX: ffffffff854c7d3c
> RDX: 0000000000000000 RSI: ffffffff854c7d46 RDI: 0000000000000006
> RBP: ffff88808b4975d0 R08: ffff88808620e540 R09: 0000000000000028
> R10: ffffed1011692f01 R11: ffff88808b49780f R12: 0000000000000008
> R13: 0000000000000028 R14: ffff888088a0cb10 R15: 0000000000000000
> FS:  00000000006de940(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004c4d28 CR3: 0000000090d8e000 CR4: 00000000001406e0
> Call Trace:
>   binder_alloc_copy_from_buffer+0x37/0x42 drivers/android/binder_alloc.c:1187
>   binder_get_object+0xc3/0x200 drivers/android/binder.c:2062
>   binder_transaction+0x2b4a/0x6690 drivers/android/binder.c:3231
>   binder_thread_write+0x87e/0x2820 drivers/android/binder.c:3781
>   binder_ioctl_write_read drivers/android/binder.c:4825 [inline]
>   binder_ioctl+0x1033/0x183b drivers/android/binder.c:5002
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   file_ioctl fs/ioctl.c:509 [inline]
>   do_vfs_ioctl+0xd6e/0x1390 fs/ioctl.c:696
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>   __do_sys_ioctl fs/ioctl.c:720 [inline]
>   __se_sys_ioctl fs/ioctl.c:718 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x445f19
> Code: e8 7c e7 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 db cb fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fffeaa7b578 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000445f19
> RDX: 0000000020000240 RSI: 00000000c0306201 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000403010
> R10: 00007fffeaa7b0d0 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000403010 R14: 0000000000000000 R15: 0000000000000000
> Modules linked in:
> ---[ end trace 0f3d90ce4ca56ff6 ]---
> RIP: 0010:binder_alloc_do_buffer_copy+0xd6/0x510
> drivers/android/binder_alloc.c:1141
> Code: 02 00 0f 85 20 04 00 00 4d 8b 64 24 58 49 29 dc e8 4f f4 23 fc 4c 89
> e6 4c 89 ef e8 64 f5 23 fc 4d 39 e5 76 07 e8 3a f4 23 fc <0f> 0b e8 33 f4
> 23 fc 4c 8b 75 d0 4d 29 ec 4c 89 e6 4c 89 f7 e8 41
> RSP: 0018:ffff88808b497550 EFLAGS: 00010293
> RAX: ffff88808620e540 RBX: 0000000020001000 RCX: ffffffff854c7d3c
> RDX: 0000000000000000 RSI: ffffffff854c7d46 RDI: 0000000000000006
> RBP: ffff88808b4975d0 R08: ffff88808620e540 R09: 0000000000000028
> R10: ffffed1011692f01 R11: ffff88808b49780f R12: 0000000000000008
> R13: 0000000000000028 R14: ffff888088a0cb10 R15: 0000000000000000
> FS:  00000000006de940(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004c4d28 CR3: 0000000090d8e000 CR4: 00000000001406f0
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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From d49c95c944c15732ef57f1c876e24838b2ddf34b Mon Sep 17 00:00:00 2001
From: Todd Kjos <tkjos@google.com>
Date: Tue, 19 Mar 2019 09:53:01 -0700
Subject: [PATCH] binder: fix BUG_ON found by selinux-testsuite

The selinux-testsuite found an issue resulting in a BUG_ON()
where a conditional relied on a size_t going negative when
checking the validity of a buffer offset.

Fixes: 7a67a39320df ("binder: add function to copy binder object from buffer")
Reported-by: Paul Moore <paul@paul-moore.com>
Tested-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
---
Please add to 5.1 (fixes problem introduced in 5.1-rc1)

 drivers/android/binder.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 8685882da64cd..4b9c7ca492e6d 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2057,7 +2057,8 @@ static size_t binder_get_object(struct binder_proc *proc,
 	size_t object_size = 0;
 
 	read_size = min_t(size_t, sizeof(*object), buffer->data_size - offset);
-	if (read_size < sizeof(*hdr) || !IS_ALIGNED(offset, sizeof(u32)))
+	if (offset > buffer->data_size || read_size < sizeof(*hdr) ||
+	    !IS_ALIGNED(offset, sizeof(u32)))
 		return 0;
 	binder_alloc_copy_from_buffer(&proc->alloc, object, buffer,
 				      offset, read_size);
-- 
2.21.0.225.g810b269d1ac-goog