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[209.85.208.182]) by smtp.gmail.com with ESMTPSA id e14-v6sm4783371ljl.43.2018.11.16.08.57.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Nov 2018 08:57:14 -0800 (PST) Received: by mail-lj1-f182.google.com with SMTP id t22-v6so20900935lji.7 for ; Fri, 16 Nov 2018 08:57:14 -0800 (PST) X-Received: by 2002:a2e:9983:: with SMTP id w3-v6mr7116901lji.133.1542387433572; Fri, 16 Nov 2018 08:57:13 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Fri, 16 Nov 2018 10:56:56 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: Oops: 0003 [#1] PREEMPT SMP NOPTI To: kyle.leet@gmail.com Cc: Linux List Kernel Mailing Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 15, 2018 at 8:29 PM Kyle Sanderson wrote: > > 2008(!) dual-core Atom box. > [1027541.963573] BUG: unable to handle kernel paging request at ffffffffb0428a44 > [1027541.963647] IP: format_decode+0x20/0x3d0 The code decodes to: 0: 55 push %rbp 1: 48 8d 2e lea (%rsi),%rbp 4: 53 push %rbx 5: 48 8d 1f lea (%rdi),%rbx 8: 48 8d 64 24 f8 lea -0x8(%rsp),%rsp d: 0f b6 06 movzbl (%rsi),%eax 10: 48 89 3c 24 mov %rdi,(%rsp) 14: 3c 01 cmp $0x1,%al 16: 74 4c je 0x64 18: 3c 02 cmp $0x2,%al 1a: 0f 84 a2 01 00 00 je 0x1c2 20:* c6 06 00 movb $0x0,(%rsi) <-- trapping instruction 23: 0f b6 07 movzbl (%rdi),%eax 26: 84 c0 test %al,%al 28: 0f 84 db 02 00 00 je 0x309 and that trapping instruction is, as far as I can tell, this one: /* By default */ spec->type = FORMAT_TYPE_NONE; and the fault seems to be a protection fault due to a write to a read-only area (and yes, we *have* read from that 'spec' pointer before that write. > [1027541.965114] RIP: 0010:format_decode+0x20/0x3d0 > [1027541.965463] Call Trace: > [1027541.965501] vsnprintf+0x56/0x4d0 This is all very odd, because that "spec" pointer points to an automatic variable on the stack of the vsnprintf() function, but we have: RSP: ffff9e8c02267ba0 RSI: ffffffffb0428a44 so it looks like some completely crazy register state corruption. Is this repeatable at all? Do you see other random faults? Linus