Sorry, I'll report later.
I will be offline until Jan. 5, 2006.
-- Takata
From: Andrew Morton <[email protected]>
Date: Tue, 27 Dec 2005 05:22:14 -0800
> Hirokazu Takata <[email protected]> wrote:
> >
> > I tried the latter way as the following patch, but the result was not
> > so gratifying; some hangups/lockups or kernel panics happened unexpectedly.
> >
> > Am I missing anything?
> > Any more comments or suggestions will be greatly appreciated.
> >
> > ...
> > --- linux-2.6.15-rc7.orig/arch/m32r/kernel/sys_m32r.c 2005-12-27 10:33:05.301372856 +0900
> > +++ linux-2.6.15-rc7/arch/m32r/kernel/sys_m32r.c 2005-12-27 10:33:10.222624712 +0900
> > @@ -29,44 +29,31 @@
> >
> > /*
> > * sys_tas() - test-and-set
> > - * linuxthreads testing version
> > */
> > -#ifndef CONFIG_SMP
> > asmlinkage int sys_tas(int *addr)
> > {
> > int oldval;
> > - unsigned long flags;
> >
> > if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
> > return -EFAULT;
> > - local_irq_save(flags);
> > - oldval = *addr;
> > - if (!oldval)
> > - *addr = 1;
> > - local_irq_restore(flags);
> > - return oldval;
> > -}
> > -#else /* CONFIG_SMP */
> > -#include <linux/spinlock.h>
> > -
> > -static DEFINE_SPINLOCK(tas_lock);
> > -
> > -asmlinkage int sys_tas(int *addr)
> > -{
> > - int oldval;
> >
> > - if (!access_ok(VERIFY_WRITE, addr, sizeof (int)))
> > - return -EFAULT;
> > -
> > - _raw_spin_lock(&tas_lock);
> > - oldval = *addr;
> > - if (!oldval)
> > - *addr = 1;
> > - _raw_spin_unlock(&tas_lock);
> > + for ( ; ; ) {
> > + get_user(oldval, addr);
>
> We need to check for -EFAULT here and fail the syscall if a fault was
> detected. Without this we'll certainly get lockups if the user passed a
> bad address. But this doesn't seem sufficient to eplain the problems which
> you've observed.
>
>
-
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