From 3435938f43ca3737ec1d73da4d8cad756b5c9508 Mon Sep 17 00:00:00 2001

From: "Richard W.M. Jones" <rjones@redhat.com>

Date: Fri, 26 Mar 2021 16:04:43 +0000

Subject: [PATCH] daemon: chroot: Fix long-standing possible deadlock.

The child (chrooted) process wrote its answer on the pipe and then

exited.  Meanwhile the parent waiting for the child to exit before

reading from the pipe.  Thus if the output was larger than a Linux

pipebuffer then the whole thing would deadlock.

(cherry picked from commit 94e64b28bee3b8dc7ed354a366d6a8f7ba5f245c)

---

 daemon/chroot.ml | 8 ++++----

 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/daemon/chroot.ml b/daemon/chroot.ml

index 5e856c91f..7da8ae29e 100644

--- a/daemon/chroot.ml

+++ b/daemon/chroot.ml

@@ -62,6 +62,10 @@ let f t func arg =

   (* Parent. *)

   close wfd;

+  let chan = in_channel_of_descr rfd in

+  let ret = input_value chan in

+  close_in chan;

+

   let _, status = waitpid [] pid in

   (match status with

    | WEXITED 0 -> ()

@@ -76,10 +80,6 @@ let f t func arg =

       failwithf "chroot ‘%s’ stopped by signal %d" t.name i

   );

-  let chan = in_channel_of_descr rfd in

-  let ret = input_value chan in

-  close_in chan;

-

   match ret with

   | Either ret -> ret

   | Or exn -> raise exn

-- 

2.18.4