uprobes/x86: Fix arch_uprobe_disable_step() && UTASK_SSTEP_TRAPPED interaction

arch_uprobe_disable_step() should also take UTASK_SSTEP_TRAPPED into
account. In this case the probed insn was not executed, we need to
clear X86_EFLAGS_TF if it was set by us and that is all.

Again, this code will look more clean when we move it into
arch_uprobe_post_xol() and arch_uprobe_abort_xol().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 7e993d1f1992..9538f00827a9 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -706,14 +706,20 @@ void arch_uprobe_disable_step(struct arch_uprobe *auprobe)
 {
         struct task_struct *task = current;
         struct arch_uprobe_task *autask = &task->utask->autask;
+        bool trapped = (task->utask->state == UTASK_SSTEP_TRAPPED);
         struct pt_regs *regs = task_pt_regs(task);
         /*
          * The state of TIF_BLOCKSTEP was not saved so we can get an extra
          * SIGTRAP if we do not clear TF. We need to examine the opcode to
          * make it right.
          */
-        if (autask->saved_tf)
-                send_sig(SIGTRAP, task, 0);
-        else if (!(auprobe->fixups & UPROBE_FIX_SETF))
-                regs->flags &= ~X86_EFLAGS_TF;
+        if (unlikely(trapped)) {
+                if (!autask->saved_tf)
+                        regs->flags &= ~X86_EFLAGS_TF;
+        } else {
+                if (autask->saved_tf)
+                        send_sig(SIGTRAP, task, 0);
+                else if (!(auprobe->fixups & UPROBE_FIX_SETF))
+                        regs->flags &= ~X86_EFLAGS_TF;
+        }
 }