Date: Saturday, May 9, 2020 @ 19:59:26 Author: heftig Revision: 382975
5.6.11.a-3: more GCC 10 fixes Added: linux-hardened/trunk/0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch linux-hardened/trunk/0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch Modified: linux-hardened/trunk/0001-gcc-plugins-drop-support-for-GCC-4.7.patch linux-hardened/trunk/0002-gcc-common.h-Update-for-GCC-10.patch linux-hardened/trunk/PKGBUILD -----------------------------------------------------------+ 0001-gcc-plugins-drop-support-for-GCC-4.7.patch | 2 0002-gcc-common.h-Update-for-GCC-10.patch | 2 0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch | 32 ++ 0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch | 131 ++++++++++++ PKGBUILD | 10 5 files changed, 172 insertions(+), 5 deletions(-) Modified: 0001-gcc-plugins-drop-support-for-GCC-4.7.patch =================================================================== --- 0001-gcc-plugins-drop-support-for-GCC-4.7.patch 2020-05-09 19:59:23 UTC (rev 382974) +++ 0001-gcc-plugins-drop-support-for-GCC-4.7.patch 2020-05-09 19:59:26 UTC (rev 382975) @@ -1,7 +1,7 @@ From dba68a9d4df76d49d32245e4236713a43fb321da Mon Sep 17 00:00:00 2001 From: Masahiro Yamada <masahi...@kernel.org> Date: Sun, 29 Mar 2020 20:08:32 +0900 -Subject: [PATCH 1/2] gcc-plugins: drop support for GCC <= 4.7 +Subject: [PATCH 1/4] gcc-plugins: drop support for GCC <= 4.7 Nobody was opposed to raising minimum GCC version to 4.8 [1] So, we will drop GCC <= 4.7 support sooner or later. Modified: 0002-gcc-common.h-Update-for-GCC-10.patch =================================================================== --- 0002-gcc-common.h-Update-for-GCC-10.patch 2020-05-09 19:59:23 UTC (rev 382974) +++ 0002-gcc-common.h-Update-for-GCC-10.patch 2020-05-09 19:59:26 UTC (rev 382975) @@ -2,7 +2,7 @@ From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Pierret=20=28fepitre=29?= <frederic.pier...@qubes-os.org> Date: Tue, 7 Apr 2020 13:32:59 +0200 -Subject: [PATCH 2/2] gcc-common.h: Update for GCC 10 +Subject: [PATCH 2/4] gcc-common.h: Update for GCC 10 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Added: 0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch =================================================================== --- 0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch (rev 0) +++ 0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch 2020-05-09 19:59:26 UTC (rev 382975) @@ -0,0 +1,32 @@ +From af805f5f1d2e61dd2cf907d9635f0abc66fe1197 Mon Sep 17 00:00:00 2001 +From: Sergei Trofimovich <sly...@gentoo.org> +Date: Tue, 17 Mar 2020 00:07:18 +0000 +Subject: [PATCH 3/4] Makefile: disallow data races on gcc-10 as well + +gcc-10 will rename --param=allow-store-data-races=0 +to -fno-allow-store-data-races. + +The flag change happened at https://gcc.gnu.org/PR92046. + +Signed-off-by: Sergei Trofimovich <sly...@gentoo.org> +Acked-by: Jiri Kosina <jkos...@suse.cz> +Signed-off-by: Masahiro Yamada <masahi...@kernel.org> +--- + Makefile | 1 + + 1 file changed, 1 insertion(+) + +diff --git a/Makefile b/Makefile +index 5dedd6f9ad75..6899bfc9dc7b 100644 +--- a/Makefile ++++ b/Makefile +@@ -714,6 +714,7 @@ endif + + # Tell gcc to never replace conditional load with a non-conditional one + KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0) ++KBUILD_CFLAGS += $(call cc-option,-fno-allow-store-data-races) + + include scripts/Makefile.kcov + include scripts/Makefile.gcc-plugins +-- +2.26.2 + Added: 0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch =================================================================== --- 0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch (rev 0) +++ 0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch 2020-05-09 19:59:26 UTC (rev 382975) @@ -0,0 +1,131 @@ +From 309b6eca2e2605accf7a3b02b47b5c2732dbe543 Mon Sep 17 00:00:00 2001 +From: Borislav Petkov <b...@suse.de> +Date: Wed, 22 Apr 2020 18:11:30 +0200 +Subject: [PATCH 4/4] x86: Fix early boot crash on gcc-10, next try +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +... or the odyssey of trying to disable the stack protector for the +function which generates the stack canary value. + +The whole story started with Sergei reporting a boot crash with a kernel +built with gcc-10: + + Kernel panic — not syncing: stack-protector: Kernel stack is corrupted in: start_secondary + CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc5—00235—gfffb08b37df9 #139 + Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M—D3H, BIOS F12 11/14/2013 + Call Trace: + dump_stack + panic + ? start_secondary + __stack_chk_fail + start_secondary + secondary_startup_64 + -—-[ end Kernel panic — not syncing: stack—protector: Kernel stack is corrupted in: start_secondary + +This happens because gcc-10 tail-call optimizes the last function call +in start_secondary() - cpu_startup_entry() - and thus emits a stack +canary check which fails because the canary value changes after the +boot_init_stack_canary() call. + +To fix that, the initial attempt was to mark the one function which +generates the stack canary with: + + __attribute__((optimize("-fno-stack-protector"))) ... start_secondary(void *unused) + +however, using the optimize attribute doesn't work cumulatively +as the attribute does not add to but rather replaces previously +supplied optimization options - roughly all -fxxx options. + +The key one among them being -fno-omit-frame-pointer and thus leading to +not present frame pointer - frame pointer which the kernel needs. + +The next attempt to prevent compilers from tail-call optimizing +the last function call cpu_startup_entry(), shy of carving out +start_secondary() into a separate compilation unit and building it with +-fno-stack-protector, is this one. + +The current solution is short and sweet, and reportedly, is supported by +both compilers so let's see how far we'll get this time. + +Reported-by: Sergei Trofimovich <sly...@gentoo.org> +Signed-off-by: Borislav Petkov <b...@suse.de> +Reviewed-by: Nick Desaulniers <ndesaulni...@google.com> +Reviewed-by: Kees Cook <keesc...@chromium.org> +Link: https://lkml.kernel.org/r/20200314164451.346497-1-sly...@gentoo.org +--- + arch/x86/include/asm/stackprotector.h | 7 ++++++- + arch/x86/kernel/smpboot.c | 8 ++++++++ + arch/x86/xen/smp_pv.c | 1 + + include/linux/compiler.h | 6 ++++++ + 4 files changed, 21 insertions(+), 1 deletion(-) + +diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h +index 91e29b6a86a5..9804a7957f4e 100644 +--- a/arch/x86/include/asm/stackprotector.h ++++ b/arch/x86/include/asm/stackprotector.h +@@ -55,8 +55,13 @@ + /* + * Initialize the stackprotector canary value. + * +- * NOTE: this must only be called from functions that never return, ++ * NOTE: this must only be called from functions that never return + * and it must always be inlined. ++ * ++ * In addition, it should be called from a compilation unit for which ++ * stack protector is disabled. Alternatively, the caller should not end ++ * with a function call which gets tail-call optimized as that would ++ * lead to checking a modified canary value. + */ + static __always_inline void boot_init_stack_canary(void) + { +diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c +index 69881b2d446c..9674321ce3a3 100644 +--- a/arch/x86/kernel/smpboot.c ++++ b/arch/x86/kernel/smpboot.c +@@ -262,6 +262,14 @@ static void notrace start_secondary(void *unused) + + wmb(); + cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); ++ ++ /* ++ * Prevent tail call to cpu_startup_entry() because the stack protector ++ * guard has been changed a couple of function calls up, in ++ * boot_init_stack_canary() and must not be checked before tail calling ++ * another function. ++ */ ++ prevent_tail_call_optimization(); + } + + /** +diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c +index 802ee5bba66c..0cebe5db691d 100644 +--- a/arch/x86/xen/smp_pv.c ++++ b/arch/x86/xen/smp_pv.c +@@ -92,6 +92,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void) + cpu_bringup(); + boot_init_stack_canary(); + cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); ++ prevent_tail_call_optimization(); + } + + void xen_smp_intr_free_pv(unsigned int cpu) +diff --git a/include/linux/compiler.h b/include/linux/compiler.h +index 034b0a644efc..732754d96039 100644 +--- a/include/linux/compiler.h ++++ b/include/linux/compiler.h +@@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off) + /* &a[0] degrades to a pointer: a different type from an array */ + #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) + ++/* ++ * This is needed in functions which generate the stack canary, see ++ * arch/x86/kernel/smpboot.c::start_secondary() for an example. ++ */ ++#define prevent_tail_call_optimization() asm("") ++ + #endif /* __LINUX_COMPILER_H */ +-- +2.26.2 + Modified: PKGBUILD =================================================================== --- PKGBUILD 2020-05-09 19:59:23 UTC (rev 382974) +++ PKGBUILD 2020-05-09 19:59:26 UTC (rev 382975) @@ -5,7 +5,7 @@ pkgbase=linux-hardened pkgver=5.6.11.a -pkgrel=2 +pkgrel=3 pkgdesc='Security-Hardened Linux' url='https://github.com/anthraxx/linux-hardened' arch=(x86_64) @@ -22,6 +22,8 @@ config # the main kernel config file 0001-gcc-plugins-drop-support-for-GCC-4.7.patch 0002-gcc-common.h-Update-for-GCC-10.patch + 0003-Makefile-disallow-data-races-on-gcc-10-as-well.patch + 0004-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch sphinx-workaround.patch ) validpgpkeys=( @@ -35,8 +37,10 @@ 'a3eb5f89cff627b3bd9232edf50ff28a9522134e9529017b82412cb19ce3ccac' 'SKIP' '93ba919836378a3a4df05e78011281a6e4430afe89a0e54dac48e2ad15355fa4' - 'f52774d05b2ab6886df95434a31a6070799b7bcc5d48ca9c93d499d40dd9622d' - '40c9da5e310ba66c99aeb4c472c6549d8b98cb13ea66835df0291a113113b0c5' + '118531186e7069b006d48fdfb2dbd9f28ee6d01cbfaacb007d8f44e8e76a57e1' + 'd2ee933dd10dee475746a7e9081bca3ebdae8c6fb631f458d8f0d4987c9a0845' + 'b604f4041c94d12abc0a0ad9e15ab54a7712c424d7740d6dffff8e0a001ae862' + '09dbf84dff332fd9c2cde9eca97ce70e73ff7b90c08f22b169c6b69a633c56b0' '8cb21e0b3411327b627a9dd15b8eb773295a0d2782b1a41b2a8839d1b2f5778c') export KBUILD_BUILD_HOST=archlinux