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Mon, 27 Aug 2018 21:05:57 -0700 (PDT) Date: Mon, 27 Aug 2018 21:05:56 -0700 From: Alexei Starovoitov To: Steven Rostedt Cc: syzbot , linux-kernel@vger.kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, Daniel Borkmann , netdev@vger.kernel.org Subject: Re: WARNING in format_decode (2) Message-ID: <20180828040554.u5xbypakkzcibziq@ast-mbp> References: <000000000000e12d4105746dcb0d@google.com> <20180827134626.1b943593@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180827134626.1b943593@gandalf.local.home> User-Agent: NeoMutt/20180223 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 27, 2018 at 01:46:26PM -0400, Steven Rostedt wrote: > On Mon, 27 Aug 2018 10:10:04 -0700 > syzbot wrote: > > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: 2ad0d5269970 Merge git://git.kernel.org/pub/scm/linux/kern.. > > git tree: net-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=15b8efba400000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=79e695838ce7a210 > > dashboard link: https://syzkaller.appspot.com/bug?extid=1ec5c5ec949c4adaa0c4 > > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1626f761400000 > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+1ec5c5ec949c4adaa0c4@syzkaller.appspotmail.com > > > > ** ** > > ** NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE ** > > ********************************************************** > > ------------[ cut here ]------------ > > Please remove unsupported %WARNING: CPU: 0 PID: 6453 at lib/vsprintf.c:2149 format_decode+0x8fc/0xaf0 > > lib/vsprintf.c:2149 > > Kernel panic - not syncing: panic_on_warn set ... > > > > CPU: 0 PID: 6453 Comm: syz-executor7 Not tainted 4.18.0+ #190 > > 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+0x1c9/0x2b4 lib/dump_stack.c:113 > > panic+0x238/0x4e7 kernel/panic.c:184 > > __warn.cold.8+0x163/0x1ba kernel/panic.c:536 > > report_bug+0x252/0x2d0 lib/bug.c:186 > > fixup_bug arch/x86/kernel/traps.c:178 [inline] > > do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296 > > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316 > > invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:993 > > RIP: 0010:format_decode+0x8fc/0xaf0 lib/vsprintf.c:2149 > > Code: e8 59 59 c9 fa 41 c6 04 24 12 e9 94 fd ff ff e8 4a 59 c9 fa 0f be f3 > > 48 c7 c7 60 bc 89 87 c6 05 28 aa d2 01 01 e8 e4 e9 93 fa <0f> 0b 4d 8b 7d > > c0 e9 56 fe ff ff 48 8b bd 68 ff ff ff e8 cd 4f 08 > > RSP: 0018:ffff8801b6b27688 EFLAGS: 00010282 > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: ffffffff816422b1 RDI: ffff8801b6b27378 > > RBP: ffff8801b6b27730 R08: ffff8801b69a0040 R09: 0000000000000006 > > R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801b6b277a8 > > R13: ffff8801b6b27708 R14: 0000000000000000 R15: ffff8801b6b27b04 > > vsnprintf+0x185/0x1b60 lib/vsprintf.c:2245 > > vscnprintf+0x2d/0x80 lib/vsprintf.c:2396 > > __trace_array_vprintk.part.60+0xc7/0x330 kernel/trace/trace.c:2990 > > __trace_array_vprintk kernel/trace/trace.c:3021 [inline] > > trace_array_vprintk kernel/trace/trace.c:3021 [inline] > > trace_vprintk+0x5f/0x90 kernel/trace/trace.c:3059 > > __trace_printk+0xce/0x120 kernel/trace/trace_printk.c:237 > > ____bpf_trace_printk kernel/trace/bpf_trace.c:274 [inline] > > Looks like a bug in the bpf trace printk code. yes. looks like %p% slipped past bpf_trace_printk() runtime checks.