[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZynDAhW0lKCfOqZl@kernel.org>
Date: Tue, 5 Nov 2024 09:02:26 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Luis Chamberlain <mcgrof@...nel.org>,
Andreas Larsson <andreas@...sler.com>,
Andy Lutomirski <luto@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Brian Cain <bcain@...cinc.com>,
Catalin Marinas <catalin.marinas@....com>,
Christoph Hellwig <hch@...radead.org>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Dinh Nguyen <dinguyen@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Guo Ren <guoren@...nel.org>, Helge Deller <deller@....de>,
Huacai Chen <chenhuacai@...nel.org>, Ingo Molnar <mingo@...hat.com>,
Johannes Berg <johannes@...solutions.net>,
John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
Kent Overstreet <kent.overstreet@...ux.dev>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Mark Rutland <mark.rutland@....com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Matt Turner <mattst88@...il.com>, Max Filippov <jcmvbkbc@...il.com>,
Michael Ellerman <mpe@...erman.id.au>,
Michal Simek <monstr@...str.eu>, Oleg Nesterov <oleg@...hat.com>,
Palmer Dabbelt <palmer@...belt.com>,
Peter Zijlstra <peterz@...radead.org>,
Richard Weinberger <richard@....at>,
Russell King <linux@...linux.org.uk>, Song Liu <song@...nel.org>,
Stafford Horne <shorne@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Uladzislau Rezki <urezki@...il.com>,
Vineet Gupta <vgupta@...nel.org>, Will Deacon <will@...nel.org>,
bpf@...r.kernel.org, linux-alpha@...r.kernel.org,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
linux-mips@...r.kernel.org, linux-mm@...ck.org,
linux-modules@...r.kernel.org, linux-openrisc@...r.kernel.org,
linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-sh@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
linux-trace-kernel@...r.kernel.org, linux-um@...ts.infradead.org,
linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v7 6/8] x86/module: prepare module loading for ROX
allocations of text
Hi Nathan,
On Mon, Nov 04, 2024 at 04:27:41PM -0700, Nathan Chancellor wrote:
> Hi Mike,
>
> On Wed, Oct 23, 2024 at 07:27:09PM +0300, Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
> >
> > When module text memory will be allocated with ROX permissions, the
> > memory at the actual address where the module will live will contain
> > invalid instructions and there will be a writable copy that contains the
> > actual module code.
> >
> > Update relocations and alternatives patching to deal with it.
> >
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> > Tested-by: kdevops <kdevops@...ts.linux.dev>
>
> Hopefully the last time you have to hear from me, as I am only
> experiencing issues with only one of my test machines at this point and
> it is my only machine that supports IBT, so it seems to point to
> something specific with the IBT part of the FineIBT support. I notice
> either a boot hang or an almost immediate reboot (triple fault?). I
> guess this is how I missed reporting this earlier, as my machine was
> falling back to the default distribution kernel after the restart and I
> did not notice I was not actually testing a -next kernel.
>
> Checking out the version of this change that is in next-20241104, commit
> 7ca6ed09db62 ("x86/module: prepare module loading for ROX allocations of
> text"), it boots with either 'cfi=off' or 'cfi=kcfi' but it exhibits the
> issues noted above with 'cfi=fineibt'. At the immediate parent, commit
> b575d981092f ("arch: introduce set_direct_map_valid_noflush()"), all
> three combinations boot fine.
>
> $ uname -r; tr ' ' '\n' </proc/cmdline | grep cfi=
>
> 6.12.0-rc5-debug-00214-g7ca6ed09db62
> cfi=kcfi
>
> 6.12.0-rc5-debug-00214-g7ca6ed09db62
> cfi=off
>
> 6.12.0-rc5-debug-00213-gb575d981092f
> cfi=fineibt
>
> 6.12.0-rc5-debug-00213-gb575d981092f
> cfi=kcfi
>
> 6.12.0-rc5-debug-00213-gb575d981092f
> cfi=off
>
> I do not think this machine has an accessible serial port and I do not
> think IBT virtualization is supported via either KVM or TCG in QEMU, so
> I am not sure how to get more information about what is going on here. I
> wanted to try reverting these changes on top of next-20241104 but there
> was a non-trivial conflict in mm/execmem.c due to some changes on top,
> so I just tested in the mm history.
>
> If there is any other information I can provide or patches I can test, I
> am more than happy to do so.
Yes, please :)
There's a silly mistake in cfi_rewrite_endbr() in that commit, the patch
below should fix it. Can you please test?
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 3407efc26528..243843e44e89 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1241,7 +1241,7 @@ static void cfi_rewrite_endbr(s32 *start, s32 *end, struct module *mod)
void *addr = (void *)s + *s;
void *wr_addr = module_writable_address(mod, addr);
- poison_endbr(addr+16, wr_addr, false);
+ poison_endbr(addr + 16, wr_addr + 16, false);
}
}
> Cheers,
> Nathan
--
Sincerely yours,
Mike.
Powered by blists - more mailing lists