diff options
Diffstat (limited to '0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch')
| -rw-r--r-- | 0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch | 131 |
1 files changed, 0 insertions, 131 deletions
diff --git a/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch b/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch deleted file mode 100644 index 140111c..0000000 --- a/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch +++ /dev/null @@ -1,131 +0,0 @@ -From 309b6eca2e2605accf7a3b02b47b5c2732dbe543 Mon Sep 17 00:00:00 2001 -From: Borislav Petkov <bp@suse.de> -Date: Wed, 22 Apr 2020 18:11:30 +0200 -Subject: 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 <slyfox@gentoo.org> -Signed-off-by: Borislav Petkov <bp@suse.de> -Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> -Reviewed-by: Kees Cook <keescook@chromium.org> -Link: https://lkml.kernel.org/r/20200314164451.346497-1-slyfox@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 */ --- -cgit v1.2.3-1-gf6bb5 - |