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uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails

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Currently the error from arch_uprobe_post_xol() is silently ignored.
This doesn't look good and this can lead to the hard-to-debug problems.

1. Change handle_singlestep() to loudly complain and send SIGILL.

   Note: this only affects x86, ppc/arm can't fail.

2. Change arch_uprobe_post_xol() to call arch_uprobe_abort_xol() and
   avoid TF games if it is going to return an error.

   This can help to to analyze the problem, if nothing else we should
   not report ->ip = xol_slot in the core-file.

   Note: this means that handle_riprel_post_xol() can be called twice,
   but this is fine because it is idempotent.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
This commit is contained in:
Oleg Nesterov
2014-04-03 20:20:10 +02:00
parent e55848a4f8
commit 014940bad8
2 changed files with 19 additions and 5 deletions
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16
arch/x86/kernel/uprobes.c
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@@ -594,6 +594,15 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
struct uprobe_task *utask = current->utask;
WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
if (auprobe->ops->post_xol) {
int err = auprobe->ops->post_xol(auprobe, regs);
if (err) {
arch_uprobe_abort_xol(auprobe, regs);
return err;
}
}
current->thread.trap_nr = utask->autask.saved_trap_nr;
/*
* arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
@@ -605,8 +614,6 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
else if (!(auprobe->fixups & UPROBE_FIX_SETF))
regs->flags &= ~X86_EFLAGS_TF;
if (auprobe->ops->post_xol)
return auprobe->ops->post_xol(auprobe, regs);
return 0;
}
@@ -641,8 +648,9 @@ int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val,
/*
* This function gets called when XOL instruction either gets trapped or
* the thread has a fatal signal, so reset the instruction pointer to its
* probed address.
* the thread has a fatal signal, or if arch_uprobe_post_xol() failed.
* Reset the instruction pointer to its probed address for the potential
* restart or for post mortem analysis.
*/
void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{