On Tue, Mar 10, 2020 at 9:10 AM Dmitry Vyukov <[email protected]> wrote: > > On Tue, Mar 10, 2020 at 7:15 AM Nathan Chancellor > <[email protected]> wrote: > > > > On Mon, Mar 09, 2020 at 09:20:58AM +0100, Dmitry Vyukov wrote: > > > On Sun, Mar 8, 2020 at 7:35 PM 'Jann Horn' via syzkaller-bugs > > > <[email protected]> wrote: > > > > > > > > On Sun, Mar 8, 2020 at 5:40 PM syzbot > > > > <[email protected]> wrote: > > > > > HEAD commit: 63623fd4 Merge tag 'for-linus' of > > > > > git://git.kernel.org/pub.. > > > > > git tree: upstream > > > > > console output: > > > > > https://syzkaller.appspot.com/x/log.txt?x=16cfeac3e00000 > > > > > kernel config: > > > > > https://syzkaller.appspot.com/x/.config?x=5d2e033af114153f > > > > > dashboard link: > > > > > https://syzkaller.appspot.com/bug?extid=cd66e43794b178bb5cd6 > > > > > compiler: clang version 10.0.0 > > > > > (https://github.com/llvm/llvm-project/ > > > > > c2443155a0fb245c8f17f2c1c72b6ea391e86e81) > > > > > syz repro: > > > > > https://syzkaller.appspot.com/x/repro.syz?x=12a42329e00000 > > > > > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the > > > > > commit: > > > > > Reported-by: [email protected] > > > > > > > > > > general protection fault, probably for non-canonical address > > > > > 0x1ffffffff1255a6b: 0000 [#1] PREEMPT SMP KASAN > > > > > CPU: 0 PID: 8742 Comm: syz-executor.2 Not tainted 5.6.0-rc3-syzkaller > > > > > #0 > > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, > > > > > BIOS Google 01/01/2011 > > > > > RIP: 0010:arch_local_irq_disable arch/x86/include/asm/paravirt.h:757 > > > > > [inline] > > > > > RIP: 0010:syscall_return_slowpath+0xeb/0x4a0 > > > > > arch/x86/entry/common.c:277 > > > > > Code: 00 10 0f 85 de 00 00 00 e8 b2 a3 76 00 48 c7 c0 58 d3 2a 89 48 > > > > > c1 e8 03 80 3c 18 00 74 0c 48 c7 c7 58 d3 2a 89 e8 05 00 00 00 <00> > > > > > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > > > > RSP: 0018:ffffc900020a7ed0 EFLAGS: 00010246 > > > > > RAX: 1ffffffff1255a6b RBX: dffffc0000000000 RCX: ffff88808c512380 > > > > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > > > > > RBP: ffffc900020a7f10 R08: ffffffff810075bb R09: fffffbfff14d9182 > > > > > R10: fffffbfff14d9182 R11: 0000000000000000 R12: 1ffff110118a2470 > > > > > R13: 0000000000004000 R14: ffff88808c512380 R15: ffff88808c512380 > > > > > FS: 000000000154f940(0000) GS:ffff8880aea00000(0000) > > > > > knlGS:0000000000000000 > > > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > > > CR2: 000000000076c000 CR3: 00000000a6b05000 CR4: 00000000001406f0 > > > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > > > Call Trace: > > > > > do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:304 > > > > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > > > > > #PF: supervisor write access in kernel mode > > > > > #PF: error_code(0x0002) - not-present page > > > > > PGD 8fecc067 P4D 8fecc067 PUD 97953067 PMD 0 > > > > > Oops: 0002 [#2] PREEMPT SMP KASAN > > > > > CPU: 0 PID: 8742 Comm: syz-executor.2 Not tainted 5.6.0-rc3-syzkaller > > > > > #0 > > > > > > > > Ugh, why does it build with -Werror... > > > > There are certain warnings that are specifically treated like errors: > > > > In the main Makefile: > > > > KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) > > > > > Now I am realizing I don't know what's the proper way to turn off > > > warnings entirely... > > > > > > We turn off this CONFIG_ERROR_ON_WARNING historically: > > > https://github.com/google/syzkaller/blob/2e9971bbbfb4df6ba0118353163a7703f3dbd6ec/dashboard/config/bits-syzbot.config#L17 > > > and I thought that's enough. But now I realize it's not even a thing. > > > I see it referenced in some ChromeOS threads and there are some > > > discussions re upstreaming, but apparently it never existed upstream. > > > > > > make has W=n, but it seems that it can only be used to produce more > > > warnings. We don't pass W=3 specifically and there is no W=0. > > > > > > Should we always build with CFLAGS=-w? Is it guaranteed to work? Or is > > > there a better way? > > > > Would passing -Wno-werror via KCFLAGS work? Otherwise, passing > > -Wno-error=<specific warning> should work. > > > > Cheers, > > Nathan > > Filed https://github.com/google/syzkaller/issues/1635 so that this is not > lost.
Jann, Getting back to this. Are you sure building without warning will be better? Currently make enables these warnings as errors only: -Werror=strict-prototypes -Werror=implicit-function-declaration -Werror=implicit-int -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init So most warnings won't cause build failure. And, say, converting T* to Y* implicitly may be an actual bug in the patch. The other concern is that some people may use syzbot testing as the only patch testing and then submit a patch that breaks build...
