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From: Will Deacon <will@kernel.org>
To: Liam Howlett <liam.howlett@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Julien Grall <julien.grall@arm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>
Subject: Re: [PATCH 1/3] arm64: armv8_deprecated: Fix swp_handler() signal generation
Date: Thu, 22 Apr 2021 13:59:04 +0100	[thread overview]
Message-ID: <20210422125903.GD1521@willie-the-truck> (raw)
In-Reply-To: <20210420165001.3790670-1-Liam.Howlett@Oracle.com>

On Tue, Apr 20, 2021 at 04:50:12PM +0000, Liam Howlett wrote:
> arm64_notify_segfault() was written to decide on the si_code from the
> assembly emulation of the swp_handler(), but was also used for the
> signal generation from failed access_ok() and unaligned instructions.
> 
> When access_ok() fails, there is no need to search for the offending
> address in the VMA space.  Instead, simply set the error to SIGSEGV with
> si_code SEGV_ACCERR.
> 
> Change the return code from emulate_swpX() when there is an unaligned
> pointer so the caller can differentiate from the EFAULT.  It is
> unnecessary to search the VMAs in the case of an unaligned pointer.
> This change uses SIGSEGV and SEGV_ACCERR instead of SIGBUS to keep with
> what was returned before.
> 
> Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm)
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
>  arch/arm64/kernel/armv8_deprecated.c | 20 +++++++++++++-------

Can you give an example of something that is fixed by this, please? At first
glance, it doesn't look like it changes the user-visible behaviour.

We should also be compatible with arch/arm/ here (see set_segfault()).

Will

WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Liam Howlett <liam.howlett@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Julien Grall <julien.grall@arm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>
Subject: Re: [PATCH 1/3] arm64: armv8_deprecated: Fix swp_handler() signal generation
Date: Thu, 22 Apr 2021 13:59:04 +0100	[thread overview]
Message-ID: <20210422125903.GD1521@willie-the-truck> (raw)
In-Reply-To: <20210420165001.3790670-1-Liam.Howlett@Oracle.com>

On Tue, Apr 20, 2021 at 04:50:12PM +0000, Liam Howlett wrote:
> arm64_notify_segfault() was written to decide on the si_code from the
> assembly emulation of the swp_handler(), but was also used for the
> signal generation from failed access_ok() and unaligned instructions.
> 
> When access_ok() fails, there is no need to search for the offending
> address in the VMA space.  Instead, simply set the error to SIGSEGV with
> si_code SEGV_ACCERR.
> 
> Change the return code from emulate_swpX() when there is an unaligned
> pointer so the caller can differentiate from the EFAULT.  It is
> unnecessary to search the VMAs in the case of an unaligned pointer.
> This change uses SIGSEGV and SEGV_ACCERR instead of SIGBUS to keep with
> what was returned before.
> 
> Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm)
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> ---
>  arch/arm64/kernel/armv8_deprecated.c | 20 +++++++++++++-------

Can you give an example of something that is fixed by this, please? At first
glance, it doesn't look like it changes the user-visible behaviour.

We should also be compatible with arch/arm/ here (see set_segfault()).

Will

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  parent reply	other threads:[~2021-04-22 12:59 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20 16:50 [PATCH 1/3] arm64: armv8_deprecated: Fix swp_handler() signal generation Liam Howlett
2021-04-20 16:50 ` Liam Howlett
2021-04-20 16:50 ` [PATCH 2/3] arm64: signal: sigreturn() and rt_sigreturn() sometime returns the wrong signals Liam Howlett
2021-04-20 16:50   ` Liam Howlett
2021-04-22 12:48   ` Will Deacon
2021-04-22 12:48     ` Will Deacon
2021-04-22 18:22     ` Eric W. Biederman
2021-04-22 18:22       ` Eric W. Biederman
2021-04-22 19:24       ` Liam Howlett
2021-04-22 19:24         ` Liam Howlett
2021-04-23 18:17         ` Eric W. Biederman
2021-04-23 18:17           ` Eric W. Biederman
2021-04-23 20:03           ` Liam Howlett
2021-04-23 20:03             ` Liam Howlett
2021-04-29 17:52             ` Eric W. Biederman
2021-04-29 17:52               ` Eric W. Biederman
2021-04-30 18:48               ` Liam Howlett
2021-04-30 18:48                 ` Liam Howlett
2021-04-30 19:57                 ` Eric W. Biederman
2021-04-30 19:57                   ` Eric W. Biederman
2021-04-30 20:31                   ` Liam Howlett
2021-04-30 20:31                     ` Liam Howlett
2021-04-20 16:50 ` [PATCH 3/3] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code Liam Howlett
2021-04-20 16:50   ` Liam Howlett
2021-04-22 12:53   ` Will Deacon
2021-04-22 12:53     ` Will Deacon
2021-04-22 18:56     ` Liam Howlett
2021-04-22 18:56       ` Liam Howlett
2021-04-20 21:22 ` [PATCH 1/3] arm64: armv8_deprecated: Fix swp_handler() signal generation kernel test robot
2021-04-20 21:22   ` kernel test robot
2021-04-21 15:47   ` Liam Howlett
2021-04-21 15:47     ` Liam Howlett
2021-04-21 15:47     ` Liam Howlett
2021-04-22 12:59 ` Will Deacon [this message]
2021-04-22 12:59   ` Will Deacon
2021-04-23  1:00   ` Liam Howlett
2021-04-23  1:00     ` Liam Howlett

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