linux-kernel - [PATCH RFC v2 1/4] exec: add a flag indicating if an exec file is a suid/sgid

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Date:   Tue, 28 Dec 2021 14:09:05 -0300
From:   Wander Lairson Costa <wander@...hat.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Laurent Vivier <laurent@...ier.eu>,
        YunQiang Su <ysu@...ecomp.com>, Helge Deller <deller@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Alexey Gladkov <legion@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Rolf Eike Beer <eb@...ix.com>,
        linux-fsdevel@...r.kernel.org (open list:FILESYSTEMS (VFS and
        infrastructure)), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH RFC v2 1/4] exec: add a flag indicating if an exec file is a suid/sgid

We create an additional flag in the struct linux_bprm to indicate a
suid/sgid binary. We will use this information in a later commit to
set the task_struct flags accordingly.

Signed-off-by: Wander Lairson Costa <wander@...hat.com>
---
 fs/exec.c               | 2 ++
 include/linux/binfmts.h | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 537d92c41105..ec07b36fdbb4 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1619,11 +1619,13 @@ static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
 	if (mode & S_ISUID) {
 		bprm->per_clear |= PER_CLEAR_ON_SETID;
 		bprm->cred->euid = uid;
+		bprm->suid_bin = 1;
 	}
 
 	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
 		bprm->per_clear |= PER_CLEAR_ON_SETID;
 		bprm->cred->egid = gid;
+		bprm->suid_bin = 1;
 	}
 }
 
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 049cf9421d83..c4b41b9711d2 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -41,7 +41,11 @@ struct linux_binprm {
 		 * Set when errors can no longer be returned to the
 		 * original userspace.
 		 */
-		point_of_no_return:1;
+		point_of_no_return:1,
+		/*
+		 * Is this a suid/sgid binary?
+		 */
+		suid_bin:1;
 #ifdef __alpha__
 	unsigned int taso:1;
 #endif
-- 
2.27.0