Patch "Revert "exec: avoid RLIMIT_STACK races with prlimit()"" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Revert "exec: avoid RLIMIT_STACK races with prlimit()"

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     revert-exec-avoid-rlimit_stack-races-with-prlimit.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 779f4e1c6c7c661db40dfebd6dd6bda7b5f88aa3 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Tue, 12 Dec 2017 11:28:38 -0800
Subject: Revert "exec: avoid RLIMIT_STACK races with prlimit()"
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From: Kees Cook <keescook@chromium.org>

commit 779f4e1c6c7c661db40dfebd6dd6bda7b5f88aa3 upstream.

This reverts commit 04e35f4495dd560db30c25efca4eecae8ec8c375.

SELinux runs with secureexec for all non-"noatsecure" domain transitions,
which means lots of processes end up hitting the stack hard-limit change
that was introduced in order to fix a race with prlimit(). That race fix
will need to be redesigned.

Reported-by: Laura Abbott <labbott@redhat.com>
Reported-by: Tomáš Trnka <trnka@scm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/exec.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1340,15 +1340,10 @@ void setup_new_exec(struct linux_binprm
 		 * avoid bad behavior from the prior rlimits. This has to
 		 * happen before arch_pick_mmap_layout(), which examines
 		 * RLIMIT_STACK, but after the point of no return to avoid
-		 * races from other threads changing the limits. This also
-		 * must be protected from races with prlimit() calls.
+		 * needing to clean up the change on failure.
 		 */
-		task_lock(current->group_leader);
 		if (current->signal->rlim[RLIMIT_STACK].rlim_cur > _STK_LIM)
 			current->signal->rlim[RLIMIT_STACK].rlim_cur = _STK_LIM;
-		if (current->signal->rlim[RLIMIT_STACK].rlim_max > _STK_LIM)
-			current->signal->rlim[RLIMIT_STACK].rlim_max = _STK_LIM;
-		task_unlock(current->group_leader);
 	}
 
 	arch_pick_mmap_layout(current->mm);


Patches currently in stable-queue which might be from keescook@chromium.org are

queue-4.14/revert-exec-avoid-rlimit_stack-races-with-prlimit.patch
queue-4.14/string.h-workaround-for-increased-stack-usage.patch
queue-4.14/arm64-fix-config_debug_wx-address-reporting.patch