KASAN: use-after-free Read in dev_uevent

syzbot
2020-06-19T05:48:17Z

Hello,

syzbot found the following crash on:

HEAD commit: 7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=169fa049100000
kernel config: https://syzkaller.appspot.com/x/.config?x=be4578b3f1083656
dashboard link: https://syzkaller.appspot.com/bug?extid=348b571beb5eeb70a582
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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+348b571beb5eeb70a582@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in dev_uevent+0x30a/0x580 drivers/base/core.c:1486
Read of size 8 at addr ffff888098662098 by task systemd-udevd/29958

CPU: 0 PID: 29958 Comm: systemd-udevd Not tainted 5.7.0-syzkaller #0
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+0x1e9/0x30e lib/dump_stack.c:118
print_address_description+0x66/0x5a0 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
dev_uevent+0x30a/0x580 drivers/base/core.c:1486
uevent_show+0x1b2/0x2f0 drivers/base/core.c:1557
dev_attr_show+0x50/0xc0 drivers/base/core.c:1261
sysfs_kf_seq_show+0x30e/0x4e0 fs/sysfs/file.c:60
seq_read+0x41a/0xce0 fs/seq_file.c:208
__vfs_read+0x9c/0x6d0 fs/read_write.c:426
vfs_read+0x1c4/0x400 fs/read_write.c:462
ksys_read+0x11b/0x220 fs/read_write.c:588
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x7f28fc677910
Code: b6 fe ff ff 48 8d 3d 0f be 08 00 48 83 ec 08 e8 06 db 01 00 66 0f 1f 44 00 00 83 3d f9 2d 2c 00 00 75 10 b8 00 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 de 9b 01 00 48 89 04 24
RSP: 002b:00007ffe3053dd18 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00005562a17eb920 RCX: 00007f28fc677910
RDX: 0000000000001000 RSI: 00005562a17fe8c0 RDI: 0000000000000007
RBP: 00007f28fc932440 R08: 00007f28fc9361e8 R09: 0000000000001010
R10: 00005562a17eb920 R11: 0000000000000246 R12: 0000000000001000
R13: 0000000000000d68 R14: 00005562a17fe8c0 R15: 00007f28fc931900

Allocated by task 29904:
save_stack mm/kasan/common.c:48 [inline]
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
dev_new drivers/usb/gadget/legacy/raw_gadget.c:182 [inline]
raw_open+0x87/0x500 drivers/usb/gadget/legacy/raw_gadget.c:372
misc_open+0x346/0x3c0 drivers/char/misc.c:141
chrdev_open+0x498/0x580 fs/char_dev.c:414
do_dentry_open+0x808/0x1020 fs/open.c:828
do_open fs/namei.c:3229 [inline]
path_openat+0x2790/0x38b0 fs/namei.c:3346
do_filp_open+0x191/0x3a0 fs/namei.c:3373
do_sys_openat2+0x463/0x770 fs/open.c:1179
do_sys_open fs/open.c:1195 [inline]
ksys_open include/linux/syscalls.h:1388 [inline]
__do_sys_open fs/open.c:1201 [inline]
__se_sys_open fs/open.c:1199 [inline]
__x64_sys_open+0x1af/0x1e0 fs/open.c:1199
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 29956:
save_stack mm/kasan/common.c:48 [inline]
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x220 mm/slab.c:3757
raw_release+0x130/0x1e0 drivers/usb/gadget/legacy/raw_gadget.c:411
__fput+0x2ed/0x750 fs/file_table.c:281
task_work_run+0x147/0x1d0 kernel/task_work.c:123
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x5ef/0x1f80 kernel/exit.c:806
do_group_exit+0x15e/0x2c0 kernel/exit.c:904
get_signal+0x13cf/0x1d60 kernel/signal.c:2739
do_signal+0x33/0x610 arch/x86/kernel/signal.c:810
exit_to_usermode_loop arch/x86/entry/common.c:161 [inline]
prepare_exit_to_usermode+0x32a/0x600 arch/x86/entry/common.c:196
entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff888098662000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 152 bytes inside of
4096-byte region [ffff888098662000, ffff888098663000)
The buggy address belongs to the page:
page:ffffea0002619880 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0002619880 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00021d0908 ffffea0002a5a808 ffff8880aa402000
raw: 0000000000000000 ffff888098662000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888098661f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888098662000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888098662080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888098662100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888098662180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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