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Revert "x86: signal: change type of paramter for sys_rt_sigreturn()"

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This reverts commit 4217458daf.

Justin Madru bisected this commit, it was causing weird Firefox
crashes.

The reason is that GCC mis-optimizes (re-uses) the on-stack parameters of
the calling frame, which corrupts the syscall return pt_regs state and
thus corrupts user-space register state.

So we go back to the slightly less clean but more optimization-safe
method of getting to pt_regs. Also add a comment to explain this.

Resolves: http://bugzilla.kernel.org/show_bug.cgi?id=12505

Reported-and-bisected-by: Justin Madru <jdm64@gawab.com>
Tested-by: Justin Madru <jdm64@gawab.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2009-01-20 09:31:49 +01:00
parent e0a96129db
commit 552b8aa4d1
2 changed files with 10 additions and 3 deletions
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2
arch/x86/include/asm/syscalls.h
View file

@ -40,7 +40,7 @@ asmlinkage int sys_sigaction(int, const struct old_sigaction __user *,
struct old_sigaction __user *);
asmlinkage int sys_sigaltstack(unsigned long);
asmlinkage unsigned long sys_sigreturn(unsigned long);
asmlinkage int sys_rt_sigreturn(struct pt_regs);
asmlinkage int sys_rt_sigreturn(unsigned long);
/* kernel/ioport.c */
asmlinkage long sys_iopl(unsigned long);

11
arch/x86/kernel/signal.c
View file

@ -632,9 +632,16 @@ badframe:
}
#ifdef CONFIG_X86_32
asmlinkage int sys_rt_sigreturn(struct pt_regs regs)
/*
* Note: do not pass in pt_regs directly as with tail-call optimization
* GCC will incorrectly stomp on the caller's frame and corrupt user-space
* register state:
*/
asmlinkage int sys_rt_sigreturn(unsigned long __unused)
{
return do_rt_sigreturn(&regs);
struct pt_regs *regs = (struct pt_regs *)&__unused;
return do_rt_sigreturn(regs);
}
#else /* !CONFIG_X86_32 */
asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)