KASAN: global-out-of-bounds Read in detach_capi_ctr

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=111be455b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=9d567e08d3970bfd8271
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9d567e...@syzkaller.appspotmail.com

platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
Bluetooth: Found 0 CAPI controller(s) on device 10:aa:aa:aa:aa:aa
==================================================================
BUG: KASAN: global-out-of-bounds in detach_capi_ctr+0xaf/0x120 drivers/isdn/capi/kcapi.c:568
Read of size 8 at addr ffffffff8dd14538 by task kcmtpd_ctr_0/25564

CPU: 1 PID: 25564 Comm: kcmtpd_ctr_0 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x5/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
detach_capi_ctr+0xaf/0x120 drivers/isdn/capi/kcapi.c:568
cmtp_session+0x162e/0x19e0 net/bluetooth/cmtp/core.c:316
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the variable:
capi_applications+0x798/0x7a0

Memory state around the buggy address:
ffffffff8dd14400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
IPVS: ftp: loaded support on port[0] = 21
ffffffff8dd14480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff8dd14500: 00 00 00 00 fa fa fa fa 00 00 00 00 00 00 00 00
^
ffffffff8dd14580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffffff8dd14600: 00 00 00 00 00 00 00 00 fa fa fa fa 00 fa fa fa
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y

console output: https://syzkaller.appspot.com/x/log.txt?x=16db5f3db00000

kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=9d567e08d3970bfd8271
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=126396ceb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17091df9b00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9d567e...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21

Bluetooth: hci0: command 0x0409 tx timeout
Bluetooth: hci0: command 0x041b tx timeout

Bluetooth: Found 0 CAPI controller(s) on device 10:aa:aa:aa:aa:aa
==================================================================
BUG: KASAN: global-out-of-bounds in detach_capi_ctr+0xaf/0x120 drivers/isdn/capi/kcapi.c:568

Read of size 8 at addr ffffffff8dd14538 by task kcmtpd_ctr_0/8156

CPU: 0 PID: 8156 Comm: kcmtpd_ctr_0 Not tainted 4.19.211-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x5/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
detach_capi_ctr+0xaf/0x120 drivers/isdn/capi/kcapi.c:568
cmtp_session+0x162e/0x19e0 net/bluetooth/cmtp/core.c:316
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the variable:
capi_applications+0x798/0x7a0

Memory state around the buggy address:
ffffffff8dd14400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00