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From: Adrian Reber <areber@redhat.com>
To: "Christian Brauner" <christian.brauner@ubuntu.com>,
	"Eric Biederman" <ebiederm@xmission.com>,
	"Pavel Emelyanov" <ovzxemul@gmail.com>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Dmitry Safonov" <0x7f454c46@gmail.com>,
	"Andrei Vagin" <avagin@gmail.com>,
	"Nicolas Viennot" <Nicolas.Viennot@twosigma.com>,
	"Michał Cłapiński" <mclapinski@google.com>,
	"Kamil Yurtsever" <kyurtsever@google.com>,
	"Dirk Petersen" <dipeit@gmail.com>,
	"Christine Flood" <chf@redhat.com>,
	"Casey Schaufler" <casey@schaufler-ca.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>,
	Radostin Stoyanov <rstoyanov1@gmail.com>,
	Adrian Reber <areber@redhat.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Serge Hallyn <serge@hallyn.com>,
	Stephen Smalley <stephen.smalley.work@gmail.com>,
	Sargun Dhillon <sargun@sargun.me>, Arnd Bergmann <arnd@arndb.de>,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, selinux@vger.kernel.org,
	Eric Paris <eparis@parisplace.org>, Jann Horn <jannh@google.com>,
	linux-fsdevel@vger.kernel.org
Subject: [PATCH v5 5/6] prctl: Allow checkpoint/restore capable processes to change exe link
Date: Wed, 15 Jul 2020 16:49:53 +0200	[thread overview]
Message-ID: <20200715144954.1387760-6-areber@redhat.com> (raw)
In-Reply-To: <20200715144954.1387760-1-areber@redhat.com>

From: Nicolas Viennot <Nicolas.Viennot@twosigma.com>

Allow CAP_CHECKPOINT_RESTORE capable users to change /proc/self/exe.

This commit also changes the permission error code from -EINVAL to
-EPERM for consistency with the rest of the prctl() syscall when
checking capabilities.

Signed-off-by: Nicolas Viennot <Nicolas.Viennot@twosigma.com>
Signed-off-by: Adrian Reber <areber@redhat.com>
---
 kernel/sys.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 00a96746e28a..dd59b9142b1d 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2007,12 +2007,14 @@ static int prctl_set_mm_map(int opt, const void __user *addr, unsigned long data
 
 	if (prctl_map.exe_fd != (u32)-1) {
 		/*
-		 * Make sure the caller has the rights to
-		 * change /proc/pid/exe link: only local sys admin should
-		 * be allowed to.
+		 * Check if the current user is checkpoint/restore capable.
+		 * At the time of this writing, it checks for CAP_SYS_ADMIN
+		 * or CAP_CHECKPOINT_RESTORE.
+		 * Note that a user with access to ptrace can masquerade an
+		 * arbitrary program as any executable, even setuid ones.
 		 */
-		if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
-			return -EINVAL;
+		if (!checkpoint_restore_ns_capable(current_user_ns()))
+			return -EPERM;
 
 		error = prctl_set_mm_exe_file(mm, prctl_map.exe_fd);
 		if (error)
-- 
2.26.2


  parent reply	other threads:[~2020-07-15 14:53 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-15 14:49 [PATCH v5 0/6] capabilities: Introduce CAP_CHECKPOINT_RESTORE Adrian Reber
2020-07-15 14:49 ` [PATCH v5 1/6] " Adrian Reber
2020-07-15 15:06   ` Christian Brauner
2020-07-15 14:49 ` [PATCH v5 2/6] pid: use checkpoint_restore_ns_capable() for set_tid Adrian Reber
2020-07-15 15:08   ` Christian Brauner
2020-07-15 14:49 ` [PATCH v5 3/6] pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid Adrian Reber
2020-07-15 15:08   ` Christian Brauner
2020-07-15 14:49 ` [PATCH v5 4/6] proc: allow access in init userns for map_files with CAP_CHECKPOINT_RESTORE Adrian Reber
2020-07-15 21:17   ` Cyrill Gorcunov
2020-07-16  8:51   ` Christian Brauner
2020-07-15 14:49 ` Adrian Reber [this message]
2020-07-15 15:20   ` [PATCH v5 5/6] prctl: Allow checkpoint/restore capable processes to change exe link Christian Brauner
2020-07-15 15:49     ` Nicolas Viennot
2020-07-15 14:49 ` [PATCH v5 6/6] selftests: add clone3() CAP_CHECKPOINT_RESTORE test Adrian Reber
2020-07-15 15:24   ` Christian Brauner
2020-07-18  3:24 ` [PATCH v5 0/6] capabilities: Introduce CAP_CHECKPOINT_RESTORE Serge E. Hallyn
2020-07-18 17:47   ` Christian Brauner

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