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x86: signal: check signal stack overflow properly 

Impact: cleanup

Check alternate signal stack overflow with proper stack pointer.
The stack pointer of the next signal frame is different if that
task has i387 state.

On x86_64, redzone would be included.

No need to check SA_ONSTACK if we're already using alternate signal stack.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <49C2874D.3080002@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Hiroshi Shimamoto 2009-03-19 10:56:29 -07:00 committed by Ingo Molnar
parent 7f00a2495b
commit 14fc9fbc70
1 changed files with 27 additions and 21 deletions
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48
arch/x86/kernel/signal.c
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@ -211,31 +211,27 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
{ {
/* Default to using normal stack */ /* Default to using normal stack */
unsigned long sp = regs->sp; unsigned long sp = regs->sp;
int onsigstack = on_sig_stack(sp);
#ifdef CONFIG_X86_64 #ifdef CONFIG_X86_64
/* redzone */ /* redzone */
sp -= 128; sp -= 128;
#endif /* CONFIG_X86_64 */ #endif /* CONFIG_X86_64 */
/* if (!onsigstack) {
* If we are on the alternate signal stack and would overflow it, don't. /* This is the X/Open sanctioned signal stack switching. */
* Return an always-bogus address instead so we will die with SIGSEGV. if (ka->sa.sa_flags & SA_ONSTACK) {
*/ if (sas_ss_flags(sp) == 0)
if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size))) sp = current->sas_ss_sp + current->sas_ss_size;
return (void __user *) -1L; } else {
/* This is the X/Open sanctioned signal stack switching. */
if (ka->sa.sa_flags & SA_ONSTACK) {
if (sas_ss_flags(sp) == 0)
sp = current->sas_ss_sp + current->sas_ss_size;
} else {
#ifdef CONFIG_X86_32 #ifdef CONFIG_X86_32
/* This is the legacy signal stack switching. */ /* This is the legacy signal stack switching. */
if ((regs->ss & 0xffff) != __USER_DS && if ((regs->ss & 0xffff) != __USER_DS &&
!(ka->sa.sa_flags & SA_RESTORER) && !(ka->sa.sa_flags & SA_RESTORER) &&
ka->sa.sa_restorer) ka->sa.sa_restorer)
sp = (unsigned long) ka->sa.sa_restorer; sp = (unsigned long) ka->sa.sa_restorer;
#endif /* CONFIG_X86_32 */ #endif /* CONFIG_X86_32 */
}
} }
if (used_math()) { if (used_math()) {
@ -244,12 +240,22 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
sp = round_down(sp, 64); sp = round_down(sp, 64);
#endif /* CONFIG_X86_64 */ #endif /* CONFIG_X86_64 */
*fpstate = (void __user *)sp; *fpstate = (void __user *)sp;
if (save_i387_xstate(*fpstate) < 0)
return (void __user *)-1L;
} }
return (void __user *)align_sigframe(sp - frame_size); sp = align_sigframe(sp - frame_size);
/*
* If we are on the alternate signal stack and would overflow it, don't.
* Return an always-bogus address instead so we will die with SIGSEGV.
*/
if (onsigstack && !likely(on_sig_stack(sp)))
return (void __user *)-1L;
/* save i387 state */
if (used_math() && save_i387_xstate(*fpstate) < 0)
return (void __user *)-1L;
return (void __user *)sp;
} }
#ifdef CONFIG_X86_32 #ifdef CONFIG_X86_32