WARNING in set_precision (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 47bbcd6b ANDROID: Fix massive cpufreq_times memory leaks
git tree: android-4.9
console output: https://syzkaller.appspot.com/x/log.txt?x=1036f978400000
kernel config: https://syzkaller.appspot.com/x/.config?x=f2dbd0c9dd968786
dashboard link: https://syzkaller.appspot.com/bug?extid=4d2f8b90fc6a442021b7
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1731bf94400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=140c9578400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4d2f8b...@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 3800 at lib/vsprintf.c:1938 set_precision+0x144/0x170
lib/vsprintf.c:1938
precision 1047814 too large[ 26.009041] Kernel panic - not syncing:
panic_on_warn set ...

CPU: 0 PID: 3800 Comm: syz-executor440 Not tainted 4.9.113-g47bbcd6 #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
ffff8801d97376e0 ffffffff81eb32a9 ffffffff83c48980 00000000ffffffff
0000000000000000 0000000000000000 0000000000000792 ffff8801d97377a0
ffffffff81421a55 0000000041b58ab3 ffffffff843bb788 ffffffff81421896
Call Trace:
[<ffffffff81eb32a9>] __dump_stack lib/dump_stack.c:15 [inline]
[<ffffffff81eb32a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
[<ffffffff81421a55>] panic+0x1bf/0x3bc kernel/panic.c:179
[<ffffffff81421d41>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
[<ffffffff811366e2>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
[<ffffffff81ed47f4>] set_precision+0x144/0x170 lib/vsprintf.c:1938
[<ffffffff81ede70e>] vsnprintf+0x31e/0x1840 lib/vsprintf.c:2014
[<ffffffff81edfc5d>] vscnprintf+0x2d/0x60 lib/vsprintf.c:2144
[<ffffffff8125f2d4>] vprintk_emit+0xf4/0x790 kernel/printk/printk.c:1847
[<ffffffff8125f998>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
[<ffffffff8125f9bd>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
[<ffffffff8142cbbc>] vprintk_func kernel/printk/internal.h:36 [inline]
[<ffffffff8142cbbc>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
[<ffffffff839e220a>] dns_resolver_preparse.cold.3+0x71/0x240
net/dns_resolver/dns_key.c:131
[<ffffffff81cd1fdb>] key_create_or_update+0x35b/0xac0
security/keys/key.c:855
[<ffffffff81cd6e54>] SYSC_add_key security/keys/keyctl.c:125 [inline]
[<ffffffff81cd6e54>] SyS_add_key+0x1b4/0x390 security/keys/keyctl.c:60
[<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
[<ffffffff839f9f93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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