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From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Stefan Wahren <stefan.wahren@i2se.com>,
	Eric Anholt <eric@anholt.net>, Phil Elwell <phil@raspberrypi.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Matthias Reichl <hias@horus.com>,
	linux-rpi-kernel@lists.infradead.org,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] Arm: mm: ftrace: Only set text back to ro after kernel has been marked ro
Date: Tue, 5 Dec 2017 20:09:35 +0000	[thread overview]
Message-ID: <20171205200935.GY10595@n2100.armlinux.org.uk> (raw)
In-Reply-To: <CAGXu5jJb0PCSuC4DuOkh5-901iVLcmmPpn1G7UBq3-r9DaeMvw@mail.gmail.com>

On Tue, Dec 05, 2017 at 11:35:59AM -0800, Kees Cook wrote:
> We don't _need_ to, but they're all contiguous, so the ro_perms array
> used by set_kernel_text_*() is actually only a single entry:
> 
> static struct section_perm ro_perms[] = {
>         /* Make kernel code and rodata RX (set RO). */
>         {
>                 .name   = "text/rodata RO",
>                 .start  = (unsigned long)_stext,
>                 .end    = (unsigned long)__init_begin,
> ...

Well, they may not be contiguous - it depends on DEBUG_ALIGN_RODATA.

Either way, we have __start_rodata_section_aligned, which is either
the start of the read-only data section, or the start of the first
section beyond __start_rodata if DEBUG_ALIGN_RODATA is not set.

Given that __start_rodata_section_aligned will always be less than
__init_begin, is there any reason not to make the above end at
__start_rodata_section_aligned, thereby allowing more of the read-only
data (in the case of DEBUG_ALIGN_RODATA=n) or all of the read-only
data (in the case of DEBUG_ALIGN_RODATA=y) to remain write-protected?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

WARNING: multiple messages have this Message-ID (diff)
From: linux@armlinux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] Arm: mm: ftrace: Only set text back to ro after kernel has been marked ro
Date: Tue, 5 Dec 2017 20:09:35 +0000	[thread overview]
Message-ID: <20171205200935.GY10595@n2100.armlinux.org.uk> (raw)
In-Reply-To: <CAGXu5jJb0PCSuC4DuOkh5-901iVLcmmPpn1G7UBq3-r9DaeMvw@mail.gmail.com>

On Tue, Dec 05, 2017 at 11:35:59AM -0800, Kees Cook wrote:
> We don't _need_ to, but they're all contiguous, so the ro_perms array
> used by set_kernel_text_*() is actually only a single entry:
> 
> static struct section_perm ro_perms[] = {
>         /* Make kernel code and rodata RX (set RO). */
>         {
>                 .name   = "text/rodata RO",
>                 .start  = (unsigned long)_stext,
>                 .end    = (unsigned long)__init_begin,
> ...

Well, they may not be contiguous - it depends on DEBUG_ALIGN_RODATA.

Either way, we have __start_rodata_section_aligned, which is either
the start of the read-only data section, or the start of the first
section beyond __start_rodata if DEBUG_ALIGN_RODATA is not set.

Given that __start_rodata_section_aligned will always be less than
__init_begin, is there any reason not to make the above end at
__start_rodata_section_aligned, thereby allowing more of the read-only
data (in the case of DEBUG_ALIGN_RODATA=n) or all of the read-only
data (in the case of DEBUG_ALIGN_RODATA=y) to remain write-protected?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

  reply	other threads:[~2017-12-05 20:09 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-23 17:58 [PATCH] Arm: mm: ftrace: Only set text back to ro after kernel has been marked ro Steven Rostedt
2017-08-23 17:58 ` Steven Rostedt
2017-08-23 18:20 ` Matthias Reichl
2017-08-23 18:20   ` Matthias Reichl
2017-08-23 18:48 ` Kees Cook
2017-08-23 18:48   ` Kees Cook
2017-08-23 19:03   ` Steven Rostedt
2017-08-23 19:03     ` Steven Rostedt
2017-12-05 11:47     ` Matthias Reichl
2017-12-05 11:47       ` Matthias Reichl
2017-12-05 13:14       ` Russell King - ARM Linux
2017-12-05 13:14         ` Russell King - ARM Linux
2017-12-05 13:23         ` Matthias Reichl
2017-12-05 13:23           ` Matthias Reichl
2017-12-05 13:30           ` Phil Elwell
2017-12-05 13:30             ` Phil Elwell
2017-12-05 13:36             ` Russell King - ARM Linux
2017-12-05 13:36               ` Russell King - ARM Linux
2017-12-05 19:35               ` Kees Cook
2017-12-05 19:35                 ` Kees Cook
2017-12-05 20:09                 ` Russell King - ARM Linux [this message]
2017-12-05 20:09                   ` Russell King - ARM Linux
2017-12-05 20:14                   ` Kees Cook
2017-12-05 20:14                     ` Kees Cook
2018-06-29 14:47                     ` Matthias Reichl
2018-06-29 14:47                       ` Matthias Reichl
2018-06-29 15:16                       ` Steven Rostedt
2018-06-29 15:16                         ` Steven Rostedt
2018-06-29 17:29                         ` Matthias Reichl
2018-06-29 17:29                           ` Matthias Reichl

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