diff options
| -rw-r--r-- | arch/x86/include/asm/stackprotector.h | 7 | ||||
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 8 | ||||
| -rw-r--r-- | arch/x86/xen/smp_pv.c | 1 | ||||
| -rw-r--r-- | include/linux/compiler.h | 6 | ||||
| -rw-r--r-- | init/main.c | 2 |
5 files changed, 23 insertions, 1 deletions
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 371b3a4af000..55b72ea5e01d 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 30447d210f37..66f2a950935a 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -270,6 +270,14 @@ 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 db6d90e451de..f779d2a5b04c 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -89,6 +89,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void) { cpu_bringup(); 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 3ffe3f3f7903..3b6e6522e0ec 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -382,4 +382,10 @@ unsigned long read_word_at_a_time(const void *addr) (_________p1); \ }) +/* + * 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() mb() + #endif /* __LINUX_COMPILER_H */ diff --git a/init/main.c b/init/main.c index b1ab36fe1a55..603b1ad88cb6 100644 --- a/init/main.c +++ b/init/main.c @@ -706,6 +706,8 @@ asmlinkage __visible void __init start_kernel(void) /* Do the rest non-__init'ed, we're now alive */ rest_init(); + + prevent_tail_call_optimization(); } /* Call all constructor functions linked into the kernel. */ |