KASAN: use-after-free Read in add_uevent_var

From: syzbot
Date: Sat May 04 2019 - 14:16:51 EST

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Hello,

syzbot found the following crash on:

HEAD commit: a4ccb5f9 Merge tag 'drm-fixes-2019-05-03' of git://anongit..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1205d570a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=2bd0da4b8de0b004
dashboard link: https://syzkaller.appspot.com/bug?extid=6da9575ba2db4da91831
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1769f62ca00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167ae984a00000

The bug was bisected to:

commit 0a1c7959acd9674a0e4e59f911f3e5fbf25fd693
Author: Wolfram Sang <wsa@xxxxxxxxxxxxx>
Date: Wed May 17 15:22:18 2017 +0000

gpu: drm: tc35876x: move header file out of I2C realm

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=138fe12ca00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=104fe12ca00000
console output: https://syzkaller.appspot.com/x/log.txt?x=178fe12ca00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6da9575ba2db4da91831@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 0a1c7959acd9 ("gpu: drm: tc35876x: move header file out of I2C realm")

RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000005502
RDX: 0000000000000000 RSI: 00000000080daf20 RDI: 00000000080f0f84
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
==================================================================
BUG: KASAN: use-after-free in string+0x208/0x230 lib/vsprintf.c:606
Read of size 1 at addr ffff8880a55aa200 by task syz-executor222/7839

CPU: 1 PID: 7839 Comm: syz-executor222 Not tainted 5.1.0-rc7+ #98
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+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
__asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:129
string+0x208/0x230 lib/vsprintf.c:606
vsnprintf+0xbfc/0x1af0 lib/vsprintf.c:2396
add_uevent_var+0x14d/0x310 lib/kobject_uevent.c:661
input_dev_uevent+0x163/0x890 drivers/input/input.c:1594
dev_uevent+0x312/0x580 drivers/base/core.c:1180
kobject_uevent_env+0x487/0x1030 lib/kobject_uevent.c:549
kobject_uevent+0x20/0x26 lib/kobject_uevent.c:638
kobject_cleanup lib/kobject.c:649 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x177/0x2ec lib/kobject.c:708
put_device+0x20/0x30 drivers/base/core.c:2205
input_put_device include/linux/input.h:349 [inline]
evdev_free+0x51/0x70 drivers/input/evdev.c:369
device_release+0x7d/0x210 drivers/base/core.c:1064
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
cdev_default_release+0x41/0x50 fs/char_dev.c:607
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
cdev_put.part.0+0x39/0x50 fs/char_dev.c:368
cdev_put+0x20/0x30 fs/char_dev.c:366
__fput+0x6df/0x8d0 fs/file_table.c:281
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x90a/0x2fa0 kernel/exit.c:876
do_group_exit+0x135/0x370 kernel/exit.c:980
__do_sys_exit_group kernel/exit.c:991 [inline]
__se_sys_exit_group kernel/exit.c:989 [inline]
__ia32_sys_exit_group+0x44/0x50 kernel/exit.c:989
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7ff7849
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000fff2db8c EFLAGS: 00000292 ORIG_RAX: 00000000000000fc
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000080f1298
RDX: 0000000000000000 RSI: 00000000080daf1c RDI: 00000000080f12a0
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7839:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_kmalloc mm/kasan/common.c:497 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:511
__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc_track_caller+0x158/0x740 mm/slab.c:3742
kstrndup+0x5f/0xf0 mm/util.c:96
uinput_dev_setup+0x1d4/0x310 drivers/input/misc/uinput.c:475
uinput_ioctl_handler.isra.0+0x12b8/0x1cc0 drivers/input/misc/uinput.c:886
uinput_compat_ioctl+0x70/0x90 drivers/input/misc/uinput.c:1062
__do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline]
__se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline]
__ia32_compat_sys_ioctl+0x197/0x620 fs/compat_ioctl.c:998
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 7839:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:459
kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
__cache_free mm/slab.c:3499 [inline]
kfree+0xcf/0x230 mm/slab.c:3822
uinput_destroy_device+0xf8/0x250 drivers/input/misc/uinput.c:311
uinput_ioctl_handler.isra.0+0x886/0x1cc0 drivers/input/misc/uinput.c:882
uinput_compat_ioctl+0x70/0x90 drivers/input/misc/uinput.c:1062
__do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline]
__se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline]
__ia32_compat_sys_ioctl+0x197/0x620 fs/compat_ioctl.c:998
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

The buggy address belongs to the object at ffff8880a55aa200
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
32-byte region [ffff8880a55aa200, ffff8880a55aa220)
The buggy address belongs to the page:
page:ffffea0002956a80 count:1 mapcount:0 mapping:ffff8880aa4001c0 index:0xffff8880a55aafc1
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002949e88 ffffea00029482c8 ffff8880aa4001c0
raw: ffff8880a55aafc1 ffff8880a55aa000 0000000100000039 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a55aa100: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8880a55aa180: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc

ffff8880a55aa200: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc

^
ffff8880a55aa280: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8880a55aa300: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

---
This bug 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@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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Previous message: Oleksij Rempel: "Re: [PATCH v3 0/3] MIPS: ath79: add ag71xx support"
Next in thread: Tetsuo Handa: "Re: KASAN: use-after-free Read in add_uevent_var"
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