From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Young Xiao <92siuyang@gmail.com>
Cc: will.deacon@arm.com, mark.rutland@arm.com, mingo@redhat.com,
bp@alien8.de, hpa@zytor.com, x86@kernel.org,
peterz@infradead.org, kan.liang@linux.intel.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf: Fix oops when kthread execs user process
Date: Tue, 28 May 2019 13:41:52 +0100 [thread overview]
Message-ID: <20190528124152.z76z7ar62hklz7tk@shell.armlinux.org.uk> (raw)
In-Reply-To: <1559046689-24091-1-git-send-email-92siuyang@gmail.com>
On Tue, May 28, 2019 at 08:31:29PM +0800, Young Xiao wrote:
> When a kthread calls call_usermodehelper() the steps are:
> 1. allocate current->mm
> 2. load_elf_binary()
> 3. populate current->thread.regs
>
> While doing this, interrupts are not disabled. If there is a perf
> interrupt in the middle of this process (i.e. step 1 has completed
> but not yet reached to step 3) and if perf tries to read userspace
> regs, kernel oops.
>
> Fix it by setting abi to PERF_SAMPLE_REGS_ABI_NONE when userspace
> pt_regs are not set.
>
> See commit bf05fc25f268 ("powerpc/perf: Fix oops when kthread execs
> user process") for details.
>
> Signed-off-by: Young Xiao <92siuyang@gmail.com>
> ---
> arch/arm/kernel/perf_regs.c | 3 ++-
> arch/arm64/kernel/perf_regs.c | 3 ++-
> arch/x86/kernel/perf_regs.c | 3 ++-
> 3 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/kernel/perf_regs.c b/arch/arm/kernel/perf_regs.c
> index 05fe92a..78ee29a 100644
> --- a/arch/arm/kernel/perf_regs.c
> +++ b/arch/arm/kernel/perf_regs.c
> @@ -36,5 +36,6 @@ void perf_get_regs_user(struct perf_regs *regs_user,
> struct pt_regs *regs_user_copy)
> {
> regs_user->regs = task_pt_regs(current);
> - regs_user->abi = perf_reg_abi(current);
> + regs_user->abi = (regs_user->regs) ? perf_reg_abi(current) :
> + PERF_SAMPLE_REGS_ABI_NONE;
I'd prefer it if we didn't introduce unnecessary parens - what function
do the parens around "regs_user->regs" serve?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2019-05-28 12:42 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 12:31 [PATCH] perf: Fix oops when kthread execs user process Young Xiao
2019-05-28 12:41 ` Russell King - ARM Linux admin [this message]
2019-05-28 14:01 ` Peter Zijlstra
2019-05-28 15:32 ` Will Deacon
2019-05-28 16:12 ` Mark Rutland
2019-05-28 17:32 ` Peter Zijlstra
2019-05-29 9:17 ` Will Deacon
2019-05-29 10:10 ` Peter Zijlstra
2019-05-29 10:20 ` Will Deacon
2019-05-29 12:55 ` Peter Zijlstra
2019-05-29 13:05 ` Will Deacon
2019-05-29 13:25 ` Peter Zijlstra
2019-05-29 14:35 ` Will Deacon
2019-05-29 16:19 ` Peter Zijlstra
2019-05-29 16:24 ` Mark Rutland
2019-05-29 16:38 ` Mark Rutland
2019-05-29 17:03 ` Peter Zijlstra
2019-05-30 10:35 ` Mark Rutland
2019-05-29 16:25 ` Will Deacon
2019-05-29 16:44 ` Peter Zijlstra
2019-05-30 7:28 ` Will Deacon
2019-05-30 8:38 ` Ravi Bangoria
2019-05-30 10:27 ` Ravi Bangoria
2019-05-31 15:37 ` Will Deacon
2019-06-03 11:23 ` Will Deacon
2019-06-03 11:48 ` Peter Zijlstra
2019-06-03 13:30 ` Michael Ellerman
2019-05-29 10:11 ` Mark Rutland
2019-05-29 4:21 ` Michael Ellerman
2019-05-29 1:44 ` Michael Ellerman
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