On Wed, Jul 20, 2022 at 11:03:24AM -0700, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: cb71b93c2dc3 Add linux-next specific files for 20220628 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=172591aa080000 > kernel config: https://syzkaller.appspot.com/x/.config?x=badbc1adb2d582eb > dashboard link: https://syzkaller.appspot.com/bug?extid=b0de012ceb1e2a97891b > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13ab4d62080000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+b0de012ceb1e2a97891b@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in usb_udc_uevent+0x11f/0x130 drivers/usb/gadget/udc/core.c:1732 > Read of size 8 at addr ffff888078ce2050 by task udevd/2968 > > CPU: 1 PID: 2968 Comm: udevd Not tainted 5.19.0-rc4-next-20220628-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > print_address_description mm/kasan/report.c:317 [inline] > print_report.cold+0x2ba/0x719 mm/kasan/report.c:433 > kasan_report+0xbe/0x1f0 mm/kasan/report.c:495 > usb_udc_uevent+0x11f/0x130 drivers/usb/gadget/udc/core.c:1732 > dev_uevent+0x290/0x770 drivers/base/core.c:2424 > uevent_show+0x1b8/0x380 drivers/base/core.c:2480 It looks like the usb_udc_uevent call races with gadget removal. The problem is that usb_udc_uevent accesses udc->driver but does not hold the udc_lock mutex (which protects this field) while doing so. Alan Stern #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/ cb71b93c2dc3 Index: usb-devel/drivers/usb/gadget/udc/core.c =================================================================== --- usb-devel.orig/drivers/usb/gadget/udc/core.c +++ usb-devel/drivers/usb/gadget/udc/core.c @@ -1728,13 +1728,14 @@ static int usb_udc_uevent(struct device return ret; } - if (udc->driver) { + mutex_lock(&udc_lock); + if (udc->driver) ret = add_uevent_var(env, "USB_UDC_DRIVER=%s", udc->driver->function); - if (ret) { - dev_err(dev, "failed to add uevent USB_UDC_DRIVER\n"); - return ret; - } + mutex_unlock(&udc_lock); + if (ret) { + dev_err(dev, "failed to add uevent USB_UDC_DRIVER\n"); + return ret; } return 0;
