Revert exec: avoid RLIMIT_STACK races with prlimit()

1 files changed, 50 insertions, 0 deletions

diff --git a/Revert-exec-avoid-RLIMIT_STACK-races-with-prlimit.patch b/Revert-exec-avoid-RLIMIT_STACK-races-with-prlimit.patch
new file mode 100644
index 000000000..0685f06aa
--- /dev/null
+++ b/Revert-exec-avoid-RLIMIT_STACK-races-with-prlimit.patch
@@ -0,0 +1,50 @@
+From patchwork Tue Dec 12 19:28:38 2017
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
+Subject: Revert "exec: avoid RLIMIT_STACK races with prlimit()"
+From: Kees Cook <keescook@chromium.org>
+X-Patchwork-Id: 10108209
+Message-Id: <20171212192838.GA14592@beast>
+To: Linus Torvalds <torvalds@linux-foundation.org>
+Cc: Laura Abbott <labbott@redhat.com>,
+ =?utf-8?B?VG9tw6HFoQ==?= Trnka <trnka@scm.com>,
+ linux-kernel@vger.kernel.org
+Date: Tue, 12 Dec 2017 11:28:38 -0800
+
+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>
+Cc: stable@vger.kernel.org
+Signed-off-by: Kees Cook <keescook@chromium.org>
+---
+ fs/exec.c | 7 +------
+ 1 file changed, 1 insertion(+), 6 deletions(-)
+
+diff --git a/fs/exec.c b/fs/exec.c
+index 6be2aa0ab26f..1d6243d9f2b6 100644
+--- a/fs/exec.c
++++ b/fs/exec.c
+@@ -1340,15 +1340,10 @@ void setup_new_exec(struct linux_binprm * bprm)
+ 		 * 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);