linux-kernel - [PATCH 3.16 201/202] apparmor: provide userspace flag indicating binfmt_elf

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Message-ID: <lsq.1556377989.763289498@decadent.org.uk>
Date:   Sat, 27 Apr 2019 16:13:09 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "John Johansen" <john.johansen@...onical.com>
Subject: [PATCH 3.16 201/202] apparmor: provide userspace flag indicating
 binfmt_elf_mmap change

3.16.66-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: John Johansen <john.johansen@...onical.com>

commit 34c426acb75cc21bdf84685e106db0c1a3565057 upstream.

Commit 9f834ec18def ("binfmt_elf: switch to new creds when switching to new mm")
changed when the creds are installed by the binfmt_elf handler. This
affects which creds are used to mmap the executable into the address
space. Which can have an affect on apparmor policy.

Add a flag to apparmor at
/sys/kernel/security/apparmor/features/domain/fix_binfmt_elf_mmap

to make it possible to detect this semantic change so that the userspace
tools and the regression test suite can correctly deal with the change.

BugLink: http://bugs.launchpad.net/bugs/1630069
Signed-off-by: John Johansen <john.johansen@...onical.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 security/apparmor/apparmorfs.c | 1 +
 1 file changed, 1 insertion(+)

--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c
@@ -794,6 +794,7 @@ static struct aa_fs_entry aa_fs_entry_do
 	AA_FS_FILE_BOOLEAN("change_hatv",	1),
 	AA_FS_FILE_BOOLEAN("change_onexec",	1),
 	AA_FS_FILE_BOOLEAN("change_profile",	1),
+	AA_FS_FILE_BOOLEAN("fix_binfmt_elf_mmap",	1),
 	{ }
 };