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

[syzbot]

Hello,

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: syzbot+3ed636...@syzkaller.appspotmail.com

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
==================================================================


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[Hillf Danton]

On Thu, 28 Jan 2021 09:08:24 -0800

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);

[Dan Carpenter]

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.

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

[Dan Carpenter]

Commit 36211f7fc1e7 ("Bluetooth: Pause service discovery for suspend")
seems like a bugfix as well but there is no Fixes tag there either. The
commit message should be more clear what the effect of the bug looks
like to the user. I like to write something like this:

[PATCH] Bluetooth: Pause service discovery for suspend

Just like MGMT_OP_START_DISCOVERY, we should reject
MGMT_OP_START_SERVICE_DISCOVERY with MGMT_STATUS_BUSY when we are paused
for suspend. This bug was discovered by auditing the software and no
one has complained about it, but presumably it leads to a hanged process
because the cmd cannot complete.

Sometimes it's hard to know what the affect of a bug is, but since
you're working in the subsystem then you probably have a better guess
than the rest of us so even a guess is useful.

regards,
dan carpenter

[Hillf Danton]

On 2 Feb 2021 15:51 Dan Carpenter wrote:

> 

>I think this was already fixed on Jan 22 commit b4a221ea8a1f ("Bluetooth:

>advmon offload MSFT add rssi support").

 

Good catch.

[syzbot]

syzbot suspects this issue was fixed by commit:

commit b4a221ea8a1f890b50838ef389d016c7ff280abc
Author: Archie Pusaka <apu...@chromium.org>
Date: Fri Jan 22 08:36:11 2021 +0000

Bluetooth: advmon offload MSFT add rssi support

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ef5ad6d00000
start commit: b491e6a7 net: lapb: Add locking to the lapb module
git tree: net

kernel config: https://syzkaller.appspot.com/x/.config?x=be33d8015c9de024
dashboard link: https://syzkaller.appspot.com/bug?extid=3ed6361bf59830ca9138

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10628ae8d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12964b80d00000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: Bluetooth: advmon offload MSFT add rssi support

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Dmitry Vyukov]

That commit touches the crashed function: