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SubjectKASAN: use-after-free Read in usb_udc_uevent
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Hello,

syzbot found the following crash on:

HEAD commit: ffeb595d Merge tag 'powerpc-5.7-6' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17f7f2b1100000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ac87c7c2ba15abf
dashboard link: https://syzkaller.appspot.com/bug?extid=b0de012ceb1e2a97891b
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+b0de012ceb1e2a97891b@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in usb_udc_uevent+0xac/0x120 drivers/usb/gadget/udc/core.c:1593
Read of size 8 at addr ffff888091a7c050 by task systemd-udevd/14223

CPU: 1 PID: 14223 Comm: systemd-udevd Not tainted 5.7.0-rc7-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+0x74/0x5c0 mm/kasan/report.c:382
__kasan_report+0x103/0x1a0 mm/kasan/report.c:511
kasan_report+0x4d/0x80 mm/kasan/common.c:625

Allocated by task 14178:
save_stack mm/kasan/common.c:49 [inline]
set_track mm/kasan/common.c:57 [inline]
__kasan_kmalloc+0x114/0x160 mm/kasan/common.c:495
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+0x82e/0x10b0 fs/open.c:797
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:1148
do_sys_open fs/open.c:1164 [inline]
ksys_open include/linux/syscalls.h:1386 [inline]
__do_sys_open fs/open.c:1170 [inline]
__se_sys_open fs/open.c:1168 [inline]
__x64_sys_open+0x1af/0x1e0 fs/open.c:1168
do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 14174:
save_stack mm/kasan/common.c:49 [inline]
set_track mm/kasan/common.c:57 [inline]
kasan_set_free_info mm/kasan/common.c:317 [inline]
__kasan_slab_free+0x125/0x190 mm/kasan/common.c:456
__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:280
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:796
do_group_exit+0x15e/0x2c0 kernel/exit.c:894
get_signal+0x13cf/0x1d60 kernel/signal.c:2739
do_signal+0x33/0x610 arch/x86/kernel/signal.c:784
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 ffff888091a7c000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 80 bytes inside of
4096-byte region [ffff888091a7c000, ffff888091a7d000)
The buggy address belongs to the page:
page:ffffea0002469f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0002469f00 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0001043588 ffffea0001258b88 ffff8880aa402000
raw: 0000000000000000 ffff888091a7c000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888091a7bf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888091a7bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888091a7c000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888091a7c080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888091a7c100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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