On Mon, Jun 24, 2019 at 2:59 PM Bjørn Mork <bjorn@xxxxxxx> wrote: > > syzbot <syzbot+b68605d7fadd21510de1@xxxxxxxxxxxxxxxxxxxxxxxxx> writes: > > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: 9939f56e usb-fuzzer: main usb gadget fuzzer driver > > git tree: https://github.com/google/kasan.git usb-fuzzer > > console output: https://syzkaller.appspot.com/x/log.txt?x=1615a669a00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=df134eda130bb43a > > dashboard link: https://syzkaller.appspot.com/bug?extid=b68605d7fadd21510de1 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10630af6a00000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1127da69a00000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+b68605d7fadd21510de1@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > usb 1-1: new high-speed USB device number 2 using dummy_hcd > > usb 1-1: Using ep0 maxpacket: 8 > > usb 1-1: New USB device found, idVendor=12d1, idProduct=14f1, > > bcdDevice=d4.d9 > > usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 > > usb 1-1: config 0 descriptor?? > > ================================================================== > > BUG: KASAN: global-out-of-bounds in qmi_wwan_probe+0x342/0x360 > > drivers/net/usb/qmi_wwan.c:1417 > > Read of size 8 at addr ffffffff8618c140 by task kworker/1:1/22 > > > > CPU: 1 PID: 22 Comm: kworker/1:1 Not tainted 5.2.0-rc5+ #11 > > Hardware name: Google Google Compute Engine/Google Compute Engine, > > BIOS Google 01/01/2011 > > Workqueue: usb_hub_wq hub_event > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0xca/0x13e lib/dump_stack.c:113 > > print_address_description+0x67/0x231 mm/kasan/report.c:188 > > __kasan_report.cold+0x1a/0x32 mm/kasan/report.c:317 > > kasan_report+0xe/0x20 mm/kasan/common.c:614 > > qmi_wwan_probe+0x342/0x360 drivers/net/usb/qmi_wwan.c:1417 > > usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361 > > really_probe+0x281/0x660 drivers/base/dd.c:509 > > driver_probe_device+0x104/0x210 drivers/base/dd.c:670 > > __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:777 > > bus_for_each_drv+0x15c/0x1e0 drivers/base/bus.c:454 > > > > Hello Kristian! > > I need some help understanding this... IIUC syzbot is claiming an > out-of-bounds access at line 1417 in v5.2-rc5. Or whatever - I'm having > a hard time deciphering what kernel version the bot is actually > testing. The claimed HEAD is not a kernel commit. At least not in my > kernel... The bot currently tests this tree: https://github.com/google/kasan/tree/usb-fuzzer, which is essentially 5.2-rc5. > > > But if this is correct, then it points to the info->data access you > recently added: > > 822e44b45eb99 (Kristian Evensen 2019-03-02 13:32:26 +0100 1409) /* Several Quectel modems supports dynamic interface configuration, so > 7c5cca3588545 (Kristian Evensen 2018-09-08 13:50:48 +0200 1410) * we need to match on class/subclass/protocol. These values are > 7c5cca3588545 (Kristian Evensen 2018-09-08 13:50:48 +0200 1411) * identical for the diagnostic- and QMI-interface, but bNumEndpoints is > 7c5cca3588545 (Kristian Evensen 2018-09-08 13:50:48 +0200 1412) * different. Ignore the current interface if the number of endpoints > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1413) * equals the number for the diag interface (two). > 7c5cca3588545 (Kristian Evensen 2018-09-08 13:50:48 +0200 1414) */ > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1415) info = (void *)&id->driver_info; > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1416) > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1417) if (info->data & QMI_WWAN_QUIRK_QUECTEL_DYNCFG) { > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1418) if (desc->bNumEndpoints == 2) > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1419) return -ENODEV; > e4bf63482c309 (Kristian Evensen 2019-04-07 15:39:09 +0200 1420) } > > > I must be blind. I cannot see how this could end up failing. > id->driver_info is always set to one of qmi_wwan_info, > qmi_wwan_info_quirk_dtr or qmi_wwan_info_quirk_quectel_dyncfg at this > point. How does that end up out-of-bounds? I've run the reproducer locally and checked the addresses. The structures that you mentioned are at: gef> p &qmi_wwan_info $1 = (const struct driver_info *) 0xffffffff85d32e80 <qmi_wwan_info> gef> p &qmi_wwan_info_quirk_dtr $2 = (const struct driver_info *) 0xffffffff85d32dc0 <qmi_wwan_info_quirk_dtr> gef> p &qmi_wwan_info_quirk_quectel_dyncfg $3 = (const struct driver_info *) 0xffffffff85d32d00 <qmi_wwan_info_quirk_quectel_dyncfg> And the bad access for me happens on address 0xffffffff85d32ce0, so it seems that driver_info somehow ended up lying below qmi_wwan_info_quirk_quectel_dyncfg. gef> x/6gx 0xffffffff85d32ce0 0xffffffff85d32ce0: 0x0000000000000000 0x0000000000000000 0xffffffff85d32cf0: 0x0000000000000000 0x0000000000000000 0xffffffff85d32d00 <qmi_wwan_info_quirk_quectel_dyncfg>: 0xffffffff85d32cc0 0x0000000000000600 > > > > Bjørn
