From: Ondrej Mosnacek <omosnace@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
selinux@vger.kernel.org, linux-security-module@vger.kernel.org,
James Morris <jmorris@namei.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] debugfs: fix security_locked_down() call for SELinux
Date: Fri, 7 May 2021 14:53:04 +0200 [thread overview]
Message-ID: <20210507125304.144394-1-omosnace@redhat.com> (raw)
When (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) is zero, then
the SELinux implementation of the locked_down hook might report a denial
even though the operation would actually be allowed.
To fix this, make sure that security_locked_down() is called only when
the return value will be taken into account (i.e. when changing one of
the problematic attributes).
Note: this was introduced by commit 5496197f9b08 ("debugfs: Restrict
debugfs when the kernel is locked down"), but it didn't matter at that
time, as the SELinux support came in later.
Fixes: 59438b46471a ("security,lockdown,selinux: implement SELinux lockdown")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---
v2: try to explain the problem better in the description
fs/debugfs/inode.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 22e86ae4dd5a..bbfc7898c1aa 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -45,10 +45,13 @@ static unsigned int debugfs_allow = DEFAULT_DEBUGFS_ALLOW_BITS;
static int debugfs_setattr(struct user_namespace *mnt_userns,
struct dentry *dentry, struct iattr *ia)
{
- int ret = security_locked_down(LOCKDOWN_DEBUGFS);
+ int ret;
- if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
- return ret;
+ if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
+ ret = security_locked_down(LOCKDOWN_DEBUGFS);
+ if (ret)
+ return ret;
+ }
return simple_setattr(&init_user_ns, dentry, ia);
}
--
2.31.1
reply other threads:[~2021-05-07 12:53 UTC|newest]
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