Messages in this thread Patch in this message | | | Subject | Re: KASAN: use-after-free Read in usb_free_coherent | From | Suzuki K Poulose <> | Date | Thu, 1 Aug 2019 11:52:01 +0100 |
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Hi
On 01/08/2019 11:38, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 7f7867ff 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=13efa030600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=792eb47789f57810 > dashboard link: https://syzkaller.appspot.com/bug?extid=d1fedb1c1fdb07fca507 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+d1fedb1c1fdb07fca507@syzkaller.appspotmail.com > > ================================================================== > BUG: KASAN: use-after-free in usb_free_coherent+0x79/0x80 > drivers/usb/core/usb.c:928 > Read of size 8 at addr ffff8881b18599c8 by task syz-executor.4/16007 > > CPU: 0 PID: 16007 Comm: syz-executor.4 Not tainted 5.3.0-rc2+ #23 > 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+0xca/0x13e lib/dump_stack.c:113 > print_address_description+0x6a/0x32c mm/kasan/report.c:351 > __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482 > kasan_report+0xe/0x12 mm/kasan/common.c:612 > usb_free_coherent+0x79/0x80 drivers/usb/core/usb.c:928 > yurex_delete+0x138/0x330 drivers/usb/misc/yurex.c:100 > kref_put include/linux/kref.h:65 [inline] > yurex_release+0x66/0x90 drivers/usb/misc/yurex.c:392 > __fput+0x2d7/0x840 fs/file_table.c:280 > task_work_run+0x13f/0x1c0 kernel/task_work.c:113 > tracehook_notify_resume include/linux/tracehook.h:188 [inline] > exit_to_usermode_loop+0x1d2/0x200 arch/x86/entry/common.c:163 > prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] > syscall_return_slowpath arch/x86/entry/common.c:274 [inline] > do_syscall_64+0x45f/0x580 arch/x86/entry/common.c:299 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x413511 > Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 > 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 > 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 > RSP: 002b:00007ffc424ea2e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 > RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000413511 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000006 > RBP: 0000000000000001 R08: 0000000029a2fc22 R09: 0000000029a2fc26 > R10: 00007ffc424ea3c0 R11: 0000000000000293 R12: 000000000075c9a0 > R13: 000000000075c9a0 R14: 0000000000761938 R15: ffffffffffffffff > > Allocated by task 2776: > save_stack+0x1b/0x80 mm/kasan/common.c:69 > set_track mm/kasan/common.c:77 [inline] > __kasan_kmalloc mm/kasan/common.c:487 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:460 > kmalloc include/linux/slab.h:552 [inline] > kzalloc include/linux/slab.h:748 [inline] > usb_alloc_dev+0x51/0xf95 drivers/usb/core/usb.c:583 > hub_port_connect drivers/usb/core/hub.c:5004 [inline] > hub_port_connect_change drivers/usb/core/hub.c:5213 [inline] > port_event drivers/usb/core/hub.c:5359 [inline] > hub_event+0x15c0/0x3640 drivers/usb/core/hub.c:5441 > process_one_work+0x92b/0x1530 kernel/workqueue.c:2269 > worker_thread+0x96/0xe20 kernel/workqueue.c:2415 > kthread+0x318/0x420 kernel/kthread.c:255 > ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 > > Freed by task 16007: > save_stack+0x1b/0x80 mm/kasan/common.c:69 > set_track mm/kasan/common.c:77 [inline] > __kasan_slab_free+0x130/0x180 mm/kasan/common.c:449 > slab_free_hook mm/slub.c:1423 [inline] > slab_free_freelist_hook mm/slub.c:1470 [inline] > slab_free mm/slub.c:3012 [inline] > kfree+0xe4/0x2f0 mm/slub.c:3953 > device_release+0x71/0x200 drivers/base/core.c:1064 > kobject_cleanup lib/kobject.c:693 [inline] > kobject_release lib/kobject.c:722 [inline] > kref_put include/linux/kref.h:65 [inline] > kobject_put+0x171/0x280 lib/kobject.c:739 > put_device+0x1b/0x30 drivers/base/core.c:2213 > usb_put_dev+0x1f/0x30 drivers/usb/core/usb.c:725 > yurex_delete+0x40/0x330 drivers/usb/misc/yurex.c:95 > kref_put include/linux/kref.h:65 [inline] > yurex_release+0x66/0x90 drivers/usb/misc/yurex.c:392 > __fput+0x2d7/0x840 fs/file_table.c:280 > task_work_run+0x13f/0x1c0 kernel/task_work.c:113 > tracehook_notify_resume include/linux/tracehook.h:188 [inline] > exit_to_usermode_loop+0x1d2/0x200 arch/x86/entry/common.c:163 > prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] > syscall_return_slowpath arch/x86/entry/common.c:274 [inline] > do_syscall_64+0x45f/0x580 arch/x86/entry/common.c:299 > entry_SYSCALL_64_after_hwframe+0x49/0xbe >
Looks like the yurex_delete() drops the ref count on the dev->udev way early in the function and then later tries to see if there are any other buffers associated with it worth releasing. So, I am guessing moving the usb_put_dev(), after we have finished all that might solve the issue ?
----8>----
diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c index 7b306aa22d25..e38fe3a53c97 100644 --- a/drivers/usb/misc/yurex.c +++ b/drivers/usb/misc/yurex.c @@ -92,7 +92,6 @@ static void yurex_delete(struct kref *kref)
dev_dbg(&dev->interface->dev, "%s\n", __func__);
- usb_put_dev(dev->udev); if (dev->cntl_urb) { usb_kill_urb(dev->cntl_urb); kfree(dev->cntl_req); @@ -108,6 +107,8 @@ static void yurex_delete(struct kref *kref) dev->int_buffer, dev->urb->transfer_dma); usb_free_urb(dev->urb); } + + usb_put_dev(dev->udev); kfree(dev); }
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