|
|
@ -5197,129 +5197,3 @@ index a2adf95b3f9c..e804d9f7583a 100644
|
|
|
|
|
|
|
|
|
|
|
|
int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
|
|
|
|
int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
|
|
|
|
pgoff_t offset, unsigned long nr_to_read);
|
|
|
|
pgoff_t offset, unsigned long nr_to_read);
|
|
|
|
|
|
|
|
|
|
|
|
rom f670269a42bfdd2c83a1118cc3d1b475547eac22 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
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
... 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 fe3ab9632f3b..4f275ac7830b 100644
|
|
|
|
|
|
|
|
--- a/arch/x86/kernel/smpboot.c
|
|
|
|
|
|
|
|
+++ b/arch/x86/kernel/smpboot.c
|
|
|
|
|
|
|
|
@@ -266,6 +266,14 @@ 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 8fb8a50a28b4..f2adb63b2d7c 100644
|
|
|
|
|
|
|
|
--- a/arch/x86/xen/smp_pv.c
|
|
|
|
|
|
|
|
+++ b/arch/x86/xen/smp_pv.c
|
|
|
|
|
|
|
|
@@ -93,6 +93,7 @@ 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 */
|
|
|
|
|
|
|
|