Re: [syzbot] [usb?] KASAN: slab-out-of-bounds Read in read_descriptors (3)

[Khazhy Kumykov]

On Fri, Jul 21, 2023 at 11:10 AM Khazhy Kumykov <khazhy@xxxxxxxxxx> wrote:
>
> On Mon, Jun 19, 2023 at 7:56 PM syzbot
> <syzbot+18996170f8096c6174d0@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    40f71e7cd3c6 Merge tag 'net-6.4-rc7' of git://git.kernel.o..
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=1581445b280000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=ac246111fb601aec
> > dashboard link: https://syzkaller.appspot.com/bug?extid=18996170f8096c6174d0
> > 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=15d23487280000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16613ed3280000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/30922ad38c58/disk-40f71e7c.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/3bd12e7503b8/vmlinux-40f71e7c.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/1dcd340b18d4/bzImage-40f71e7c.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+18996170f8096c6174d0@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > ==================================================================
> > BUG: KASAN: slab-out-of-bounds in read_descriptors+0x263/0x280 drivers/usb/core/sysfs.c:883
> > Read of size 8 at addr ffff88801e78b8c8 by task udevd/5011
> >
> > CPU: 0 PID: 5011 Comm: udevd Not tainted 6.4.0-rc6-syzkaller-00195-g40f71e7cd3c6 #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> > Call Trace:
> >  <TASK>
> >  __dump_stack lib/dump_stack.c:88 [inline]
> >  dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
> >  print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
> >  print_report mm/kasan/report.c:462 [inline]
> >  kasan_report+0x11c/0x130 mm/kasan/report.c:572
>
> "src = udev->rawdescriptors[cfgno]" (so, just reading rawdescriptors)
>
> >  read_descriptors+0x263/0x280 drivers/usb/core/sysfs.c:883
> >  sysfs_kf_bin_read+0x19a/0x270 fs/sysfs/file.c:97
> >  kernfs_file_read_iter fs/kernfs/file.c:251 [inline]
> >  kernfs_fop_read_iter+0x387/0x690 fs/kernfs/file.c:280
> >  call_read_iter include/linux/fs.h:1862 [inline]
> >  new_sync_read fs/read_write.c:389 [inline]
> >  vfs_read+0x4b1/0x8a0 fs/read_write.c:470
> >  ksys_read+0x12b/0x250 fs/read_write.c:613
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > RIP: 0033:0x7f07c7916b6a
> > Code: 00 3d 00 00 41 00 75 0d 50 48 8d 3d 2d 08 0a 00 e8 ea 7d 01 00 31 c0 e9 07 ff ff ff 64 8b 04 25 18 00 00 00 85 c0 75 1b 0f 05 <48> 3d 00 f0 ff ff 76 6c 48 8b 15 8f a2 0d 00 f7 d8 64 89 02 48 83
> > RSP: 002b:00007ffdf34973d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f07c7916b6a
> > RDX: 0000000000010011 RSI: 00007ffdf3497407 RDI: 0000000000000008
> > RBP: 0000000000000008 R08: 0000000000000003 R09: f4f13e10193fbafe
> > R10: 0000000000000000 R11: 0000000000000246 R12: 000055be37470e10
> > R13: 00007ffdf34a7ae8 R14: 00007ffdf34a8138 R15: 00007ffdf3497407
> >  </TASK>
> >
> > Allocated by task 758:
> >  kasan_save_stack+0x22/0x40 mm/kasan/common.c:45
> >  kasan_set_track+0x25/0x30 mm/kasan/common.c:52
> >  ____kasan_kmalloc mm/kasan/common.c:374 [inline]
> >  ____kasan_kmalloc mm/kasan/common.c:333 [inline]
> >  __kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
> >  kasan_kmalloc include/linux/kasan.h:196 [inline]
> >  __do_kmalloc_node mm/slab_common.c:966 [inline]
> >  __kmalloc+0x5e/0x190 mm/slab_common.c:979
> >  kmalloc include/linux/slab.h:563 [inline]
> >  kzalloc include/linux/slab.h:680 [inline]
>
> kzmalloc(length) -> this length derived from dev->descriptor.bNumConfigurations
>
> The corresponding kfree is in usb_destroy_configuration (makes sense)
> - we also set rawdescriptors to NULL here. If this race was happening,
> I'd also expect some sort of null deref report...
>
> Stumbled upon https://lore.kernel.org/all/1599201467-11000-1-git-send-email-prime.zeng@xxxxxxxxxxxxx/T/,
> which suggests that we can, instead, race with a descriptor change,
> which sounds plausible - descriptor changes, bNumConfigurations no
> longer lines up with our kmalloc... so we may run past the end of it.
Ah yeah, the syzbot C repro does something like this, it has a virtual
usb and keeps changing the descs -> which may end up calling
hub_port_connect_change()
>
> Looking at hub_port_connect_change(), we seem to read directly into
> udev->descriptor, check if it changed, and if it did, set
> udev->descriptor back to the old one...? If we have an ongoing sysfs
> read, which directly touches udev->descriptor, there might be
> trouble...
>
> I see this is called in both hub_port_connect_change() and
> usb_reset_and_verify_device()... which both seem to lock the port_dev?
> ("port_dev->status_lock"). This looks like a different lock than
> usb_lock_device_interruptible would grab, maybe the code has changed
> since that was reported in 2020. But it seems to suggest we want to
> grab this lock in sysfs to safely read from udev->descriptor.
>
> (I'm not clear on when the sysfs gets added/removed, since it happens
> in usb_bus_notify()..., the above two functions that touch
> udev->descriptor don't look like they send the
> BUS_NOTIFY_ADD/DEL_DEVICE to me, so the race seems plausible)

Ah yeah - in hub_port_connect_change() we call hub_port_connect() if
the descriptor changed, which notifies us of device remove *after* we
already directly messed with udev->descriptor for a potentially live
device.

I do see there's several sysfs files that directly read
udev->descriptor with no locking - should these all need to grab the
port_dev->status_lock?

>
> >  usb_get_configuration+0x1f7/0x5170 drivers/usb/core/config.c:887
> >  usb_enumerate_device drivers/usb/core/hub.c:2407 [inline]
> >  usb_new_device+0x12b0/0x19d0 drivers/usb/core/hub.c:2545
> >  hub_port_connect drivers/usb/core/hub.c:5407 [inline]
> >  hub_port_connect_change drivers/usb/core/hub.c:5551 [inline]
> >  port_event drivers/usb/core/hub.c:5711 [inline]
> >  hub_event+0x2d9e/0x4e40 drivers/usb/core/hub.c:5793
> >  process_one_work+0x99a/0x15e0 kernel/workqueue.c:2405
> >  worker_thread+0x67d/0x10c0 kernel/workqueue.c:2552
> >  kthread+0x344/0x440 kernel/kthread.c:379
> >  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
> >
> > The buggy address belongs to the object at ffff88801e78b8c0
> >  which belongs to the cache kmalloc-8 of size 8
> > The buggy address is located 0 bytes to the right of
> >  allocated 8-byte region [ffff88801e78b8c0, ffff88801e78b8c8)
> >
> > The buggy address belongs to the physical page:
> > page:ffffea000079e2c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1e78b
> > anon flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> > page_type: 0xffffffff()
> > raw: 00fff00000000200 ffff888012441280 0000000000000000 dead000000000001
> > raw: 0000000000000000 0000000000660066 00000001ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > page_owner tracks the page as allocated
> > page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (swapper/0), ts 8298345549, free_ts 8292702290
> >  set_page_owner include/linux/page_owner.h:31 [inline]
> >  post_alloc_hook+0x2db/0x350 mm/page_alloc.c:1731
> >  prep_new_page mm/page_alloc.c:1738 [inline]
> >  get_page_from_freelist+0xf41/0x2c00 mm/page_alloc.c:3502
> >  __alloc_pages+0x1cb/0x4a0 mm/page_alloc.c:4768
> >  alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2112
> >  alloc_pages+0x233/0x270 mm/mempolicy.c:2274
> >  alloc_slab_page mm/slub.c:1851 [inline]
> >  allocate_slab+0x25f/0x390 mm/slub.c:1998
> >  new_slab mm/slub.c:2051 [inline]
> >  ___slab_alloc+0xa91/0x1400 mm/slub.c:3192
> >  __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3291
> >  __slab_alloc_node mm/slub.c:3344 [inline]
> >  slab_alloc_node mm/slub.c:3441 [inline]
> >  __kmem_cache_alloc_node+0x136/0x320 mm/slub.c:3490
> >  __do_kmalloc_node mm/slab_common.c:965 [inline]
> >  __kmalloc_node_track_caller+0x4f/0x1a0 mm/slab_common.c:986
> >  kstrdup+0x3f/0x70 mm/util.c:62
> >  kstrdup_const+0x57/0x80 mm/util.c:85
> >  kvasprintf_const+0x10c/0x190 lib/kasprintf.c:48
> >  kobject_set_name_vargs+0x5a/0x150 lib/kobject.c:267
> >  dev_set_name+0xbf/0xf0 drivers/base/core.c:3429
> >  tty_register_device_attr+0x301/0x7d0 drivers/tty/tty_io.c:3243
> > page last free stack trace:
> >  reset_page_owner include/linux/page_owner.h:24 [inline]
> >  free_pages_prepare mm/page_alloc.c:1302 [inline]
> >  free_unref_page_prepare+0x62e/0xcb0 mm/page_alloc.c:2564
> >  free_unref_page+0x33/0x370 mm/page_alloc.c:2659
> Huh, why did our page get vfree'd, when it was kmalloc'd? Maybe the
> memory was reused multiple times before generating this report...?
> >  vfree+0x180/0x7e0 mm/vmalloc.c:2798
> >  delayed_vfree_work+0x57/0x70 mm/vmalloc.c:2719
> >  process_one_work+0x99a/0x15e0 kernel/workqueue.c:2405
> >  worker_thread+0x67d/0x10c0 kernel/workqueue.c:2552
> >  kthread+0x344/0x440 kernel/kthread.c:379
> >  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
> >
> > Memory state around the buggy address:
> >  ffff88801e78b780: 00 fc fc fc fc fa fc fc fc fc fa fc fc fc fc fa
> >  ffff88801e78b800: fc fc fc fc 00 fc fc fc fc fa fc fc fc fc fa fc
> > >ffff88801e78b880: fc fc fc fa fc fc fc fc 00 fc fc fc fc 00 fc fc
> >                                               ^
> >  ffff88801e78b900: fc fc 00 fc fc fc fc fa fc fc fc fc 00 fc fc fc
> >  ffff88801e78b980: fc 00 fc fc fc fc fa fc fc fc fc 00 fc fc fc fc
> > ==================================================================
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> >
> > syzbot will keep track of this issue. See:
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> >
> > If the bug is already fixed, let syzbot know by replying with:
> > #syz fix: exact-commit-title
> >
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> >
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> >
> > If the bug is a duplicate of another bug, reply with:
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> >
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