KASAN: slab-out-of-bounds Read in corrupted (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    156c0591 Merge tag 'linux-kselftest-5.2-rc4' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13512d51a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=60564cb52ab29d5b
dashboard link: https://syzkaller.appspot.com/bug?extid=9a901acbc447313bfe3e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11a4b01ea00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9a901acbc447313bfe3e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: slab-out-of-bounds in vsnprintf+0x1727/0x19a0  
lib/vsprintf.c:2503
Read of size 8 at addr ffff8880a91c7d00 by task syz-executor.0/9821

CPU: 0 PID: 9821 Comm: syz-executor.0 Not tainted 5.2.0-rc3+ #13
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:

Allocated by task 1024:
(stack is not available)

Freed by task 2310999008:
------------[ cut here ]------------
Bad or missing usercopy whitelist? Kernel memory overwrite attempt detected  
to SLAB object 'skbuff_head_cache' (offset 24, size 1)!
WARNING: CPU: 0 PID: 9821 at mm/usercopy.c:78 usercopy_warn+0xeb/0x110  
mm/usercopy.c:78
Kernel panic - not syncing: panic_on_warn set ...
Shutting down cpus with NMI
Kernel Offset: disabled


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