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Date: Tue, 24 Oct 2017 11:09:27 +0200 From: Greg KH <gregkh@...uxfoundation.org> To: Chen Feng <puck.chen@...ilicon.com> Cc: zhaoyukun@...wei.com, tytso@....edu, arnd@...db.de, linux-kernel@...r.kernel.org, suzhuangluan@...ilicon.com, dan.zhao@...ilicon.com Subject: Re: [PATCH RFC] random: fix syzkaller fuzzer test int overflow On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote: > [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1] > Restart is not permit > ================================================================= > UBSAN: Undefined behaviour in > kernel/linux-4.4/drivers/char/random.c:676:19 > signed integer overflow: > 2147483645 + 268435455 cannot be represented in type 'int' > CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2 Does this also happen on 4.14-rc6? > TGID: 11928 Comm: syz-executor > Hardware name: hi3660 (DT) > Call trace: > [<ffffffa661090378>] dump_backtrace+0x0/0x314 > [<ffffffa66109077c>] show_stack+0x1c/0x24 > [<ffffffa66180cc54>] dump_stack+0xdc/0x130 > [<ffffffa6618833d0>] ubsan_epilogue+0x18/0x6c > [<ffffffa661883c5c>] handle_overflow+0x180/0x1d4 > [<ffffffa661883cdc>] __ubsan_handle_add_overflow+0x2c/0x34 > [<ffffffa661ab75a0>] credit_entropy_bits+0x358/0x9a8 > [<ffffffa661ab85bc>] random_ioctl+0x338/0x384 > [<ffffffa661399c74>] do_vfs_ioctl+0x60c/0xa4c > [<ffffffa66139a150>] SyS_ioctl+0x9c/0xc0 > [<ffffffa6610838b0>] el0_svc_naked+0x24/0x28 > ================================================================= > > Signed-off-by: Chen Feng <puck.chen@...ilicon.com> > Signed-off-by: Yukun Zhao <zhaoyukun@...wei.com> > --- > drivers/char/random.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 1ef2640..6f2bd6a 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -699,6 +699,11 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits) > if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig) > goto retry; > > + if (INT_MAX - nbits < r->entropy_total) { > + WARN_ON(1); Why WARN_ON()? What is that going to help with? thanks, greg k-h
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