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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Bernd Edlinger <bernd.edlinger@hotmail.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Kees Cook <keescook@chromium.org>,
        Jann Horn <jannh@google.com>,
        Christian Brauner <christian.brauner@ubuntu.com>
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Date:   Mon, 06 Apr 2020 20:32:23 -0500
In-Reply-To: <87wo6s3wxd.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's
        message of "Mon, 06 Apr 2020 20:29:50 -0500")
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Subject: [PATCH 3/3] exec: Rename the flag called_exec_mmap point_of_no_return
Sender: linux-kernel-owner@vger.kernel.org
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Update the comments and make the code easier to understand by
renaming this flag.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/exec.c               | 12 ++++++------
 include/linux/binfmts.h |  6 +++---
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 28c87020da9b..a61987d6dc33 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1300,12 +1300,12 @@ int flush_old_exec(struct linux_binprm * bprm)
 		goto out;
 
 	/*
-	 * After setting bprm->called_exec_mmap (to mark that current is
-	 * using the prepared mm now), we have nothing left of the original
-	 * process. If anything from here on returns an error, the check
-	 * in search_binary_handler() will SEGV current.
+	 * With the new mm installed it is completely impossible to
+	 * fail and return to the original process.  If anything from
+	 * here on returns an error, the check in
+	 * search_binary_handler() will SEGV current.
 	 */
-	bprm->called_exec_mmap = 1;
+	bprm->point_of_no_return = true;
 	bprm->mm = NULL;
 
 #ifdef CONFIG_POSIX_TIMERS
@@ -1694,7 +1694,7 @@ int search_binary_handler(struct linux_binprm *bprm)
 
 		read_lock(&binfmt_lock);
 		put_binfmt(fmt);
-		if (retval < 0 && bprm->called_exec_mmap) {
+		if (retval < 0 && bprm->point_of_no_return) {
 			/* we got to flush_old_exec() and failed after it */
 			read_unlock(&binfmt_lock);
 			force_sigsegv(SIGSEGV);
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 6f564b9ad882..8f479dad7931 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -46,10 +46,10 @@ struct linux_binprm {
 		 */
 		secureexec:1,
 		/*
-		 * Set by flush_old_exec, when exec_mmap has been called.
-		 * This is past the point of no return.
+		 * Set when errors can no longer be returned to the
+		 * original userspace.
 		 */
-		called_exec_mmap:1;
+		point_of_no_return:1;
 #ifdef __alpha__
 	unsigned int taso:1;
 #endif
-- 
2.25.0