From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
bpf <bpf@vger.kernel.org>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH bpf-next 0/1] arm64: Add BPF exception tables
Date: Fri, 18 Jun 2021 09:34:10 -0700 [thread overview]
Message-ID: <CAADnVQJux+8n-vpuK9FqTLuj4cXrp04pGkpvKaUdAPXLQ4c-PQ@mail.gmail.com> (raw)
In-Reply-To: <fedff32f-e511-a191-22b0-bf421bdcce2a@linux.ibm.com>
On Wed, Jun 16, 2021 at 11:58 PM Ravi Bangoria
<ravi.bangoria@linux.ibm.com> wrote:
>
> $ dmesg
> [ 166.864325] BUG: unable to handle page fault for address: 0000000000d12345
> [ 166.864336] #PF: supervisor read access in kernel mode
> [ 166.864338] #PF: error_code(0x0000) - not-present page
>
> 0xd12345 is unallocated userspace address. Similarly, I also tried with
that's unfortunately expected, since this is a user address.
> p->dte = (void *)0xffffffffc1234567 after confirming it's not allocated
> to kernel or any module address. I see the same failure with it too.
This one is surprising though. Sounds like a bug in exception table
construction. Can you debug it to see what's causing it?
First check that do_kern_addr_fault() is invoked in this case.
And then fixup_exception() and why search_bpf_extables()
cannot find it.
Separately we probably need to replace the NULL check
with addr >= TASK_SIZE_MAX to close this issue though it's a bit artificial.
WARNING: multiple messages have this Message-ID (diff)
From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <ast@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
bpf <bpf@vger.kernel.org>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Subject: Re: [PATCH bpf-next 0/1] arm64: Add BPF exception tables
Date: Fri, 18 Jun 2021 09:34:10 -0700 [thread overview]
Message-ID: <CAADnVQJux+8n-vpuK9FqTLuj4cXrp04pGkpvKaUdAPXLQ4c-PQ@mail.gmail.com> (raw)
In-Reply-To: <fedff32f-e511-a191-22b0-bf421bdcce2a@linux.ibm.com>
On Wed, Jun 16, 2021 at 11:58 PM Ravi Bangoria
<ravi.bangoria@linux.ibm.com> wrote:
>
> $ dmesg
> [ 166.864325] BUG: unable to handle page fault for address: 0000000000d12345
> [ 166.864336] #PF: supervisor read access in kernel mode
> [ 166.864338] #PF: error_code(0x0000) - not-present page
>
> 0xd12345 is unallocated userspace address. Similarly, I also tried with
that's unfortunately expected, since this is a user address.
> p->dte = (void *)0xffffffffc1234567 after confirming it's not allocated
> to kernel or any module address. I see the same failure with it too.
This one is surprising though. Sounds like a bug in exception table
construction. Can you debug it to see what's causing it?
First check that do_kern_addr_fault() is invoked in this case.
And then fixup_exception() and why search_bpf_extables()
cannot find it.
Separately we probably need to replace the NULL check
with addr >= TASK_SIZE_MAX to close this issue though it's a bit artificial.
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-06-18 16:34 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 15:21 [PATCH bpf-next 0/1] arm64: Add BPF exception tables Jean-Philippe Brucker
2020-07-28 15:21 ` Jean-Philippe Brucker
2020-07-28 15:21 ` [PATCH bpf-next 1/1] arm64: bpf: " Jean-Philippe Brucker
2020-07-28 15:21 ` Jean-Philippe Brucker
2020-07-29 17:28 ` Song Liu
2020-07-29 17:28 ` Song Liu
2020-07-29 21:29 ` Daniel Borkmann
2020-07-29 21:29 ` Daniel Borkmann
2020-07-30 8:28 ` Jean-Philippe Brucker
2020-07-30 8:28 ` Jean-Philippe Brucker
2020-07-30 12:28 ` Qian Cai
2020-07-30 12:28 ` Qian Cai
2020-07-30 14:22 ` Jean-Philippe Brucker
2020-07-30 14:22 ` Jean-Philippe Brucker
2020-07-30 19:47 ` Daniel Borkmann
2020-07-30 19:47 ` Daniel Borkmann
2020-07-30 21:14 ` Jean-Philippe Brucker
2020-07-30 21:14 ` Jean-Philippe Brucker
2020-07-30 22:45 ` Daniel Borkmann
2020-07-30 22:45 ` Daniel Borkmann
2021-06-09 12:04 ` [PATCH bpf-next 0/1] arm64: " Ravi Bangoria
2021-06-09 12:04 ` Ravi Bangoria
2021-06-11 0:12 ` Alexei Starovoitov
2021-06-11 0:12 ` Alexei Starovoitov
2021-06-17 6:58 ` Ravi Bangoria
2021-06-17 6:58 ` Ravi Bangoria
2021-06-18 16:34 ` Alexei Starovoitov [this message]
2021-06-18 16:34 ` Alexei Starovoitov
2021-06-22 7:10 ` Ravi Bangoria
2021-06-22 7:10 ` Ravi Bangoria
2021-06-22 11:00 ` [PATCH] x86 bpf: Fix extable offset calculation Ravi Bangoria
2021-06-25 4:01 ` Alexei Starovoitov
2021-06-25 6:22 ` Ravi Bangoria
2021-06-25 15:07 ` Alexei Starovoitov
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