Merge tag 'io_uring-5.13-2021-05-07' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "Mostly fixes for merge window merged code. In detail:

   - Error case memory leak fixes (Colin, Zqiang)

   - Add the tools/io_uring/ to the list of maintained files (Lukas)

   - Set of fixes for the modified buffer registration API (Pavel)

   - Sanitize io thread setup on x86 (Stefan)

   - Ensure we truncate transfer count for registered buffers (Thadeu)"

* tag 'io_uring-5.13-2021-05-07' of git://git.kernel.dk/linux-block:
  x86/process: setup io_threads more like normal user space threads
  MAINTAINERS: add io_uring tool to IO_URING
  io_uring: truncate lengths larger than MAX_RW_COUNT on provide buffers
  io_uring: Fix memory leak in io_sqe_buffers_register()
  io_uring: Fix premature return from loop and memory leak
  io_uring: fix unchecked error in switch_start()
  io_uring: allow empty slots for reg buffers
  io_uring: add more build check for uapi
  io_uring: dont overlap internal and user req flags
  io_uring: fix drain with rsrc CQEs

1 files changed, 18 insertions, 1 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 43cbfc84153a..5e1f38179f49 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -156,7 +156,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
 #endif
 
 	/* Kernel thread ? */
-	if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
+	if (unlikely(p->flags & PF_KTHREAD)) {
 		memset(childregs, 0, sizeof(struct pt_regs));
 		kthread_frame_init(frame, sp, arg);
 		return 0;
@@ -172,6 +172,23 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 #endif
 
+	if (unlikely(p->flags & PF_IO_WORKER)) {
+		/*
+		 * An IO thread is a user space thread, but it doesn't
+		 * return to ret_after_fork().
+		 *
+		 * In order to indicate that to tools like gdb,
+		 * we reset the stack and instruction pointers.
+		 *
+		 * It does the same kernel frame setup to return to a kernel
+		 * function that a kernel thread does.
+		 */
+		childregs->sp = 0;
+		childregs->ip = 0;
+		kthread_frame_init(frame, sp, arg);
+		return 0;
+	}
+
 	/* Set a new TLS for the child thread? */
 	if (clone_flags & CLONE_SETTLS)
 		ret = set_new_tls(p, tls);