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    Subject[PATCH 10/11] - UML - Don't delay segfaults
    Date
    From
    From Bodo Stroesser - This one covers the fact, that the SIGSEGV
    signal, which is created by force_sigsegv() in case of an error in
    handle_signal(), is not delivered to the user immediately. In the
    worst case it even could be masked if a sigprocmask() systemcall
    follows immediately after return from kernel. The patch is relevant
    for other architectures, too.

    Signed-off-by: Jeff Dike <jdike@addtoit.com>

    Index: 2.6.9/arch/um/kernel/signal_kern.c
    ===================================================================
    --- 2.6.9.orig/arch/um/kernel/signal_kern.c 2004-11-12 16:24:20.000000000 -0500
    +++ 2.6.9/arch/um/kernel/signal_kern.c 2004-11-12 16:24:21.000000000 -0500
    @@ -38,9 +38,9 @@
    /*
    * OK, we're invoking a handler
    */
    -static void handle_signal(struct pt_regs *regs, unsigned long signr,
    - struct k_sigaction *ka, siginfo_t *info,
    - sigset_t *oldset)
    +static int handle_signal(struct pt_regs *regs, unsigned long signr,
    + struct k_sigaction *ka, siginfo_t *info,
    + sigset_t *oldset)
    {
    unsigned long sp;
    int err;
    @@ -94,23 +94,25 @@
    recalc_sigpending();
    spin_unlock_irq(&current->sighand->siglock);
    }
    +
    + return err;
    }

    static int kern_do_signal(struct pt_regs *regs, sigset_t *oldset)
    {
    struct k_sigaction ka_copy;
    siginfo_t info;
    - int sig;
    + int sig, handled_sig = 0;

    - sig = get_signal_to_deliver(&info, &ka_copy, regs, NULL);
    - if(sig > 0){
    + while((sig = get_signal_to_deliver(&info, &ka_copy, regs, NULL)) > 0){
    + handled_sig = 1;
    /* Whee! Actually deliver the signal. */
    - handle_signal(regs, sig, &ka_copy, &info, oldset);
    - return(1);
    + if(!handle_signal(regs, sig, &ka_copy, &info, oldset))
    + break;
    }

    /* Did we come from a system call? */
    - if(PT_REGS_SYSCALL_NR(regs) >= 0){
    + if(!handled_sig && (PT_REGS_SYSCALL_NR(regs) >= 0)){
    /* Restart the system call - no handlers present */
    if(PT_REGS_SYSCALL_RET(regs) == -ERESTARTNOHAND ||
    PT_REGS_SYSCALL_RET(regs) == -ERESTARTSYS ||
    @@ -134,7 +136,7 @@
    if(current->ptrace & PT_DTRACE)
    current->thread.singlestep_syscall =
    is_syscall(PT_REGS_IP(&current->thread.regs));
    - return(0);
    + return(handled_sig);
    }

    int do_signal(void)
    -
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