Subject: Re: KASAN: slab-out-of-bounds Read in add_adv_patterns_monitor

From: Dan Carpenter <[email-masked]>
Date: Tue, 2 Feb 2021 10:51:11 +0300

Sasha, do your stable patch picker scripts look at syzbot fix commands
to select patches to back port?  In this case a bug was fixed while
adding a new feature.  No one noticed the bug fix and there was no Fixes
tag.

On Sun, Jan 31, 2021 at 06:01:54PM +0800, Hillf Danton wrote:
> On Thu, 28 Jan 2021 09:08:24 -0800
> > syzbot found the following issue on:
> > 
> > HEAD commit:    b491e6a7 net: lapb: Add locking to the lapb module
> > git tree:       net
> > console output: https://syzkaller.appspot.com/x/log.txt?x=17ba0f2cd00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=be33d8015c9de024
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3ed6361bf59830ca9138
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10628ae8d00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12964b80d00000
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: [email-masked]
> > 
> > IPVS: ftp: loaded support on port[0] = 21
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in add_adv_patterns_monitor+0x91f/0xa90 net/bluetooth/mgmt.c:4266
> > Read of size 1 at addr ffff888013251b29 by task syz-executor387/8480
> > 
> > CPU: 1 PID: 8480 Comm: syz-executor387 Not tainted 5.11.0-rc4-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:79 [inline]
> >  dump_stack+0x107/0x163 lib/dump_stack.c:120
> >  print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
> >  __kasan_report mm/kasan/report.c:396 [inline]
> >  kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
> >  add_adv_patterns_monitor+0x91f/0xa90 net/bluetooth/mgmt.c:4266
> >  hci_mgmt_cmd net/bluetooth/hci_sock.c:1603 [inline]
> >  hci_sock_sendmsg+0x1b98/0x21d0 net/bluetooth/hci_sock.c:1738
> >  sock_sendmsg_nosec net/socket.c:652 [inline]
> >  sock_sendmsg+0xcf/0x120 net/socket.c:672
> >  sock_write_iter+0x289/0x3c0 net/socket.c:999
> >  call_write_iter include/linux/fs.h:1901 [inline]
> >  new_sync_write+0x426/0x650 fs/read_write.c:518
> >  vfs_write+0x791/0xa30 fs/read_write.c:605
> >  ksys_write+0x1ee/0x250 fs/read_write.c:658
> >  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x447579
> > Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 3b 0e fc ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007ffe0f4194b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000447579
> > RDX: 0000000000000009 RSI: 0000000020000000 RDI: 0000000000000004
> > RBP: 00000000018e1914 R08: 00000000018e1914 R09: 00007ffe0f4194a0
> > R10: 00007ffe0f4194c0 R11: 0000000000000246 R12: 0000000000000004
> > R13: 0000000000000072 R14: 00000000018e1914 R15: 0000000000000000
> > 
> > Allocated by task 8480:
> >  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
> >  kasan_set_track mm/kasan/common.c:46 [inline]
> >  set_alloc_info mm/kasan/common.c:401 [inline]
> >  ____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429
> >  kmalloc include/linux/slab.h:557 [inline]
> >  hci_mgmt_cmd net/bluetooth/hci_sock.c:1508 [inline]
> >  hci_sock_sendmsg+0x9b8/0x21d0 net/bluetooth/hci_sock.c:1738
> >  sock_sendmsg_nosec net/socket.c:652 [inline]
> >  sock_sendmsg+0xcf/0x120 net/socket.c:672
> >  sock_write_iter+0x289/0x3c0 net/socket.c:999
> >  call_write_iter include/linux/fs.h:1901 [inline]
> >  new_sync_write+0x426/0x650 fs/read_write.c:518
> >  vfs_write+0x791/0xa30 fs/read_write.c:605
> >  ksys_write+0x1ee/0x250 fs/read_write.c:658
> >  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> > The buggy address belongs to the object at ffff888013251b20
> >  which belongs to the cache kmalloc-16 of size 16
> > The buggy address is located 9 bytes inside of
> >  16-byte region [ffff888013251b20, ffff888013251b30)
> > The buggy address belongs to the page:
> > page:00000000a4467645 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13251
> > flags: 0xfff00000000200(slab)
> > raw: 00fff00000000200 ffffea00004ed440 0000000300000003 ffff888010041b40
> > raw: 0000000000000000 0000000080800080 00000001ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > 
> > Memory state around the buggy address:
> >  ffff888013251a00: fb fb fc fc fb fb fc fc 00 00 fc fc fb fb fc fc
> >  ffff888013251a80: 00 00 fc fc 00 00 fc fc fb fb fc fc 00 00 fc fc
> > >ffff888013251b00: 00 00 fc fc 00 01 fc fc fb fb fc fc fa fb fc fc
> >                                   ^
> >  ffff888013251b80: 00 00 fc fc fa fb fc fc fa fb fc fc 00 00 fc fc
> >  ffff888013251c00: fa fb fc fc fa fb fc fc 00 00 fc fc fa fb fc fc
> > ==================================================================
> 
> Fix b139553db5cd ("Bluetooth: Add handler of MGMT_OP_ADD_ADV_PATTERNS_MONITOR")  
> by adding the right-hand buffer boundary check.
> 
> --- a/net/bluetooth/mgmt.c
> +++ b/net/bluetooth/mgmt.c
> @@ -4238,7 +4238,9 @@ static int add_adv_patterns_monitor(stru
>  
>  	BT_DBG("request for %s", hdev->name);
>  
> -	if (len <= sizeof(*cp) || cp->pattern_count == 0) {
> +	if (len <= sizeof(*cp) || cp->pattern_count == 0 ||
> +	    len < sizeof(*cp) + cp->pattern_count *
> +		    			sizeof(struct mgmt_adv_pattern)) {
>  		err = mgmt_cmd_status(sk, hdev->id,
>  				      MGMT_OP_ADD_ADV_PATTERNS_MONITOR,
>  				      MGMT_STATUS_INVALID_PARAMS);
> 

I think this was already fixed on Jan 22 commit b4a221ea8a1f ("Bluetooth:
advmon offload MSFT add rssi support").

	expected_size += cp->pattern_count * sizeof(struct mgmt_adv_pattern);
	if (len != expected_size) {

Now someone needs to backport it to stable.

regards,
dan carpenter