I found a problem while using sigaction structure because of problems on definition of that structure.
I found it on version 2.6.10 but it was confirmed on version 2.6.8 and 2.6.11 (so probably on other 2.6.x versions) Extract from /include/asm-i386/signal.h (lines 142-172) #ifdef __KERNEL__ struct old_sigaction { __sighandler_t sa_handler; old_sigset_t sa_mask; unsigned long sa_flags; __sigrestore_t sa_restorer; }; struct sigaction { __sighandler_t sa_handler; unsigned long sa_flags; __sigrestore_t sa_restorer; sigset_t sa_mask; /* mask last for extensibility */ }; struct k_sigaction { struct sigaction sa; }; #else /* Here we must cater to libcs that poke about in kernel headers. */ struct sigaction { union { __sighandler_t _sa_handler; void (*_sa_sigaction)(int, struct siginfo *, void *); } _u; sigset_t sa_mask; unsigned long sa_flags; void (*sa_restorer)(void); }; As you can see the order of the fields in sigaction struct defined under __KERNEL__ is: sa_handler; sa_flags; sa_restorer; sa_mask; and the order of the fields of the section for the user code is: union {...} _u; sa_mask; sa_flags; sa_restorer; The order is not the same. Now if we look at the routine that manages the sigaction (rt_sigaction) we have the following code: Extract from /kernel/signal.c (lines 2545-2573) #ifdef __ARCH_WANT_SYS_RT_SIGACTION asmlinkage long sys_rt_sigaction(int sig, const struct sigaction __user *act, struct sigaction __user *oact, size_t sigsetsize) { struct k_sigaction new_sa, old_sa; int ret = -EINVAL; /* XXX: Don't preclude handling different sized sigset_t's. */ if (sigsetsize != sizeof(sigset_t)) goto out; if (act) { if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa))) return -EFAULT; } ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL); if (!ret && oact) { if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa))) return -EFAULT; } out: return ret; } #endif /* __ARCH_WANT_SYS_RT_SIGACTION */ As you can see the algorithm that copies the values from user struct to kernel struct is copy_from_user (and copy to_user) so because the diferent definition of the structures the data goes corrupted. To solve that problem there are two solutions: - Reorder the fields on user structure (easy solution) - Change the copy_to_user and copy_from_user for code using __put_user and __get_user I think that implementing both can prevent future problems. Greets, Jordi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/