From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Jessica Yu <jeyu@kernel.org>,
linux-s390@vger.kernel.org, heiko.carstens@de.ibm.com,
Vasily Gorbik <gor@linux.ibm.com>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>
Subject: Re: [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations
Date: Wed, 22 Apr 2020 17:21:26 +0200 [thread overview]
Message-ID: <20200422172126.743908f5@thinkpad> (raw)
In-Reply-To: <20200422164037.7edd21ea@thinkpad>
On Wed, 22 Apr 2020 16:40:37 +0200
Gerald Schaefer <gerald.schaefer@de.ibm.com> wrote:
> On Fri, 17 Apr 2020 09:04:31 -0500
> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> > From: Peter Zijlstra <peterz@infradead.org>
> >
> > Because of late module patching, a livepatch module needs to be able to
> > apply some of its relocations well after it has been loaded. Instead of
> > playing games with module_{dis,en}able_ro(), use existing text poking
> > mechanisms to apply relocations after module loading.
> >
> > So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
> > two also have STRICT_MODULE_RWX.
> >
> > This will allow removal of the last module_disable_ro() usage in
> > livepatch. The ultimate goal is to completely disallow making
> > executable mappings writable.
> >
> > Also, for the late patching case, use text_mutex, which is supposed to
> > be held for all runtime text patching operations.
> >
> > [ jpoimboe: Split up patches. Use mod state to determine whether
> > memcpy() can be used. Add text_mutex. Make it build. ]
> >
> > Cc: linux-s390@vger.kernel.org
> > Cc: heiko.carstens@de.ibm.com
> > Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > ---
> > arch/s390/kernel/module.c | 125 ++++++++++++++++++++++++--------------
> > 1 file changed, 79 insertions(+), 46 deletions(-)
>
> Sorry, just noticed this. Heiko will return next month, and I'm not
> really familiar with s390 livepatching. Adding Vasily, he might
> have some more insight.
>
> So, I might be completely wrong here, but using s390_kernel_write()
> for writing to anything other than 1:1 mapped kernel, should go
> horribly wrong, as that runs w/o DAT. It would allow to bypass
> DAT write protection, which I assume is why you want to use it,
> but it should not work on module text section, as that would be
> in vmalloc space and not 1:1 mapped kernel memory.
>
> Not quite sure how to test / trigger this, did this really work for
> you on s390?
OK, using s390_kernel_write() as default write function for module
relocation seems to work fine for me, so apparently I am missing /
mixing up something. Sorry for the noise, please ignore my concern.
next prev parent reply other threads:[~2020-04-22 15:21 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 14:04 [PATCH v2 0/9] livepatch,module: Remove .klp.arch and module_disable_ro() Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 1/9] livepatch: Disallow vmlinux.ko Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 2/9] livepatch: Apply vmlinux-specific KLP relocations early Josh Poimboeuf
2020-04-20 17:57 ` Joe Lawrence
2020-04-20 18:25 ` Josh Poimboeuf
2020-04-20 19:01 ` Joe Lawrence
2020-04-20 19:11 ` Josh Poimboeuf
2020-04-20 19:49 ` Joe Lawrence
2020-04-20 19:51 ` Josh Poimboeuf
2020-04-23 1:10 ` Joe Lawrence
2020-04-21 11:54 ` Miroslav Benes
2020-04-17 14:04 ` [PATCH v2 3/9] livepatch: Remove .klp.arch Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 4/9] livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 5/9] s390: Change s390_kernel_write() return type to match memcpy() Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 6/9] s390/module: Use s390_kernel_write() for late relocations Josh Poimboeuf
2020-04-22 12:28 ` Miroslav Benes
2020-04-24 13:43 ` Josh Poimboeuf
2020-04-22 14:40 ` Gerald Schaefer
2020-04-22 15:21 ` Gerald Schaefer [this message]
2020-04-22 19:46 ` Josh Poimboeuf
2020-04-23 12:33 ` Gerald Schaefer
2020-04-23 13:22 ` Miroslav Benes
2020-04-23 14:12 ` Josh Poimboeuf
2020-04-23 18:10 ` Josh Poimboeuf
2020-04-23 23:26 ` Josh Poimboeuf
2020-04-24 2:35 ` Joe Lawrence
2020-04-24 4:12 ` Josh Poimboeuf
2020-04-24 7:20 ` Christian Borntraeger
2020-04-24 13:37 ` Josh Poimboeuf
2020-04-30 14:38 ` Joe Lawrence
2020-04-30 16:48 ` Josh Poimboeuf
2020-04-30 17:04 ` Joe Lawrence
2020-04-23 14:21 ` Joe Lawrence
2020-04-17 14:04 ` [PATCH v2 7/9] x86/module: Use text_poke() " Josh Poimboeuf
2020-04-17 14:29 ` Peter Zijlstra
2020-04-17 14:51 ` Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 8/9] livepatch: Remove module_disable_ro() usage Josh Poimboeuf
2020-04-17 14:04 ` [PATCH v2 9/9] module: Remove module_disable_ro() Josh Poimboeuf
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