On Sun, Nov 24, 2019 at 07:30:35PM +0000, Al Viro wrote: > On Sun, Nov 24, 2019 at 11:07:00AM -0800, syzbot wrote: > > syzbot has bisected this bug to: > > > > commit 77ef8f5177599efd0cedeb52c1950c1bd73fa5e3 > > Author: Chris Metcalf <cmetcalf@xxxxxxxxxx> > > Date: Mon Jan 25 20:05:34 2016 +0000 > > > > tile kgdb: fix bug in copy to gdb regs, and optimize memset > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1131bc0ee00000 > > start commit: f5b7769e Revert "debugfs: inode: debugfs_create_dir uses m.. > > git tree: upstream > > final crash: https://syzkaller.appspot.com/x/report.txt?x=1331bc0ee00000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=1531bc0ee00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=709f8187af941e84 > > dashboard link: https://syzkaller.appspot.com/bug?extid=eaeb616d85c9a0afec7d > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177f898f800000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=147eb85f800000 > > > > Reported-by: syzbot+eaeb616d85c9a0afec7d@xxxxxxxxxxxxxxxxxxxxxxxxx > > Fixes: 77ef8f517759 ("tile kgdb: fix bug in copy to gdb regs, and optimize > > memset") > > > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > Seriously? How can the commit in question (limited to arch/tile/kernel/kgdb.c) > possibly affect a bug that manages to produce a crash report with > RSP: 0018:ffffffff82e03eb8 EFLAGS: 00000282 > RAX: 0000000000000000 RBX: ffffffff82e00000 RCX: 0000000000000000 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff81088779 > RBP: ffffffff82e03eb8 R08: 0000000000000000 R09: 0000000000000001 > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff82e00000 > FS: 0000000000000000(0000) GS:ffff88021fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000c420447ff8 CR3: 0000000213184000 CR4: 00000000001406f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > in it? Unless something very odd has happened to tile, this crash has > been observed on 64bit x86; the names of registers alone are enough > to be certain of that. > > And the binaries produced by an x86 build should not be affected by any > changes in arch/tile; not unless something is very wrong with the build > system. It's not even that this commit has fixed an earlier bug that > used to mask the one manifested here - it really should have had zero > impact on x86 builds, period. > > So I'm sorry, but I'm calling bullshit. Something's quite wrong with > the bot - either its build system or the bisection process. The acid test would be: does reverting that commit make the problem go away? See, for example, https://bugzilla.kernel.org/show_bug.cgi?id=203935 Cheers ... Duncan.
