diff options
| author | Tejun Heo <tj@kernel.org> | 2009-02-11 16:31:00 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-02-11 11:33:49 +0100 |
| commit | 5c79d2a517a9905599d192db8ce77ab5f1a2faca (patch) | |
| tree | 11f550a59b9b653fbd6c54b37effbf2d4a750fb5 /arch/x86/include/asm | |
| parent | 60a5317ff0f42dd313094b88f809f63041568b08 (diff) | |
x86: fix x86_32 stack protector bugs
Impact: fix x86_32 stack protector
Brian Gerst found out that %gs was being initialized to stack_canary
instead of stack_canary - 20, which basically gave the same canary
value for all threads. Fixing this also exposed the following bugs.
* cpu_idle() didn't call boot_init_stack_canary()
* stack canary switching in switch_to() was being done too late making
the initial run of a new thread use the old stack canary value.
Fix all of them and while at it update comment in cpu_idle() about
calling boot_init_stack_canary().
Reported-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/stackprotector.h | 2 | ||||
| -rw-r--r-- | arch/x86/include/asm/system.h | 8 |
2 files changed, 4 insertions, 6 deletions
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index fa7e5bd6fbe8..c2d742c6e15f 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -85,7 +85,7 @@ static __always_inline void boot_init_stack_canary(void) static inline void setup_stack_canary_segment(int cpu) { #ifdef CONFIG_X86_32 - unsigned long canary = (unsigned long)&per_cpu(stack_canary, cpu); + unsigned long canary = (unsigned long)&per_cpu(stack_canary, cpu) - 20; struct desc_struct *gdt_table = get_cpu_gdt_table(cpu); struct desc_struct desc; diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h index 2692ee8ef031..7a80f72bec47 100644 --- a/arch/x86/include/asm/system.h +++ b/arch/x86/include/asm/system.h @@ -25,13 +25,11 @@ struct task_struct *__switch_to(struct task_struct *prev, #ifdef CONFIG_CC_STACKPROTECTOR #define __switch_canary \ - "movl "__percpu_arg([current_task])",%%ebx\n\t" \ - "movl %P[task_canary](%%ebx),%%ebx\n\t" \ - "movl %%ebx,"__percpu_arg([stack_canary])"\n\t" + "movl %P[task_canary](%[next]), %%ebx\n\t" \ + "movl %%ebx, "__percpu_arg([stack_canary])"\n\t" #define __switch_canary_oparam \ , [stack_canary] "=m" (per_cpu_var(stack_canary)) #define __switch_canary_iparam \ - , [current_task] "m" (per_cpu_var(current_task)) \ , [task_canary] "i" (offsetof(struct task_struct, stack_canary)) #else /* CC_STACKPROTECTOR */ #define __switch_canary @@ -60,9 +58,9 @@ do { \ "movl %[next_sp],%%esp\n\t" /* restore ESP */ \ "movl $1f,%[prev_ip]\n\t" /* save EIP */ \ "pushl %[next_ip]\n\t" /* restore EIP */ \ + __switch_canary \ "jmp __switch_to\n" /* regparm call */ \ "1:\t" \ - __switch_canary \ "popl %%ebp\n\t" /* restore EBP */ \ "popfl\n" /* restore flags */ \ \ |