Merge tag 'core_urgent_for_v5.11_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull syscall entry fixes from Borislav Petkov:

 - For syscall user dispatch, separate prctl operation from syscall
   redirection range specification before the API has been made official
   in 5.11.

 - Ensure tasks using the generic syscall code do trap after returning
   from a syscall when single-stepping is requested.

* tag 'core_urgent_for_v5.11_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  entry: Use different define for selector variable in SUD
  entry: Ensure trap after single-step on system call return

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index 60d2c3798ba2..0f3c307b37b3 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -127,12 +127,17 @@ static int enable_single_step(struct task_struct *child)
 		regs->flags |= X86_EFLAGS_TF;
 
 	/*
-	 * Always set TIF_SINGLESTEP - this guarantees that
-	 * we single-step system calls etc..  This will also
+	 * Always set TIF_SINGLESTEP.  This will also
 	 * cause us to set TF when returning to user mode.
 	 */
 	set_tsk_thread_flag(child, TIF_SINGLESTEP);
 
+	/*
+	 * Ensure that a trap is triggered once stepping out of a system
+	 * call prior to executing any user instruction.
+	 */
+	set_task_syscall_work(child, SYSCALL_EXIT_TRAP);
+
 	oflags = regs->flags;
 
 	/* Set TF on the kernel stack.. */
@@ -230,6 +235,7 @@ void user_disable_single_step(struct task_struct *child)
 
 	/* Always clear TIF_SINGLESTEP... */
 	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+	clear_task_syscall_work(child, SYSCALL_EXIT_TRAP);
 
 	/* But touch TF only if it was set by us.. */
 	if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))