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Message-ID: <Zwkg3LwlNJOwNWZh@kernel.org>
Date: Fri, 11 Oct 2024 15:58:04 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.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>,
Luis Chamberlain <mcgrof@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Matt Turner <mattst88@...il.com>, Max Filippov <jcmvbkbc@...il.com>,
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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>,
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,
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sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v5 6/8] x86/module: perpare module loading for ROX
allocations of text
On Thu, Oct 10, 2024 at 03:54:11PM -0700, Nathan Chancellor wrote:
> Hi Mike,
>
> On Wed, Oct 09, 2024 at 09:08:14PM +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>
>
> I bisected a boot failure that I see with CONFIG_CFI_CLANG enabled to
> this change as commit be712757cabd ("x86/module: perpare module loading
> for ROX allocations of text") in -next.
> [ 0.000000] Linux version 6.12.0-rc2-00140-gbe712757cabd (nathan@...xlarge-x86) (ClangBuiltLinux clang version 19.1.0 (https://github.com/llvm/llvm-project.git a4bf6cd7cfb1a1421ba92bca9d017b49936c55e4), ClangBuiltLinux LLD 19.1.0 (https://github.com/llvm/llvm-project.git a4bf6cd7cfb1a1421ba92bca9d017b49936c55e4)) #1 SMP PREEMPT_DYNAMIC Thu Oct 10 22:42:57 UTC 2024
> ...
> [ 0.092204] Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl
> [ 0.093207] TAA: Mitigation: TSX disabled
> [ 0.093711] MMIO Stale Data: Mitigation: Clear CPU buffers
> [ 0.094228] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
> [ 0.095203] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
> [ 0.096203] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
> [ 0.097203] x86/fpu: Supporting XSAVE feature 0x020: 'AVX-512 opmask'
> [ 0.098003] x86/fpu: Supporting XSAVE feature 0x040: 'AVX-512 Hi256'
> [ 0.098203] x86/fpu: Supporting XSAVE feature 0x080: 'AVX-512 ZMM_Hi256'
> [ 0.099203] x86/fpu: Supporting XSAVE feature 0x200: 'Protection Keys User registers'
> [ 0.100204] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256
> [ 0.101204] x86/fpu: xstate_offset[5]: 832, xstate_sizes[5]: 64
> [ 0.102203] x86/fpu: xstate_offset[6]: 896, xstate_sizes[6]: 512
> [ 0.103204] x86/fpu: xstate_offset[7]: 1408, xstate_sizes[7]: 1024
> [ 0.104051] x86/fpu: xstate_offset[9]: 2432, xstate_sizes[9]: 8
> [ 0.104204] x86/fpu: Enabled xstate features 0x2e7, context size is 2440 bytes, using 'compacted' format.
>
> then nothing after that. Boot is successful if CFI is not enabled (the
> initrd will just shutdown the machine after printing the version string).
>
> If there is any further information I can provide or patches I can test,
> I am more than happy to do so.
I overlooked how cfi_*_callers routines update addr.
This patch should fix it:
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 3b3fa93af3b1..cf782f431110 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1148,11 +1148,13 @@ static int cfi_disable_callers(s32 *start, s32 *end, struct module *mod)
for (s = start; s < end; s++) {
void *addr = (void *)s + *s;
- void *wr_addr = module_writable_address(mod, addr);
+ void *wr_addr;
u32 hash;
addr -= fineibt_caller_size;
- hash = decode_caller_hash(addr);
+ wr_addr = module_writable_address(mod, addr);
+ hash = decode_caller_hash(wr_addr);
+
if (!hash) /* nocfi callers */
continue;
@@ -1172,11 +1174,12 @@ static int cfi_enable_callers(s32 *start, s32 *end, struct module *mod)
for (s = start; s < end; s++) {
void *addr = (void *)s + *s;
- void *wr_addr = module_writable_address(mod, addr);
+ void *wr_addr;
u32 hash;
addr -= fineibt_caller_size;
- hash = decode_caller_hash(addr);
+ wr_addr = module_writable_address(mod, addr);
+ hash = decode_caller_hash(wr_addr);
if (!hash) /* nocfi callers */
continue;
@@ -1249,11 +1252,12 @@ static int cfi_rand_callers(s32 *start, s32 *end, struct module *mod)
for (s = start; s < end; s++) {
void *addr = (void *)s + *s;
- void *wr_addr = module_writable_address(mod, addr);
+ void *wr_addr;
u32 hash;
addr -= fineibt_caller_size;
- hash = decode_caller_hash(addr);
+ wr_addr = module_writable_address(mod, addr);
+ hash = decode_caller_hash(wr_addr);
if (hash) {
hash = -cfi_rehash(hash);
text_poke_early(wr_addr + 2, &hash, 4);
@@ -1269,14 +1273,15 @@ static int cfi_rewrite_callers(s32 *start, s32 *end, struct module *mod)
for (s = start; s < end; s++) {
void *addr = (void *)s + *s;
- void *wr_addr = module_writable_address(mod, addr);
+ void *wr_addr;
u32 hash;
addr -= fineibt_caller_size;
- hash = decode_caller_hash(addr);
+ wr_addr = module_writable_address(mod, addr);
+ hash = decode_caller_hash(wr_addr);
if (hash) {
text_poke_early(wr_addr, fineibt_caller_start, fineibt_caller_size);
- WARN_ON(*(u32 *)(addr + fineibt_caller_hash) != 0x12345678);
+ WARN_ON(*(u32 *)(wr_addr + fineibt_caller_hash) != 0x12345678);
text_poke_early(wr_addr + fineibt_caller_hash, &hash, 4);
}
/* rely on apply_retpolines() */
> Cheers,
> Nathan
--
Sincerely yours,
Mike.
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