From: "Serge E. Hallyn" <serge@hallyn.com>
To: lkml <linux-kernel@vger.kernel.org>
Cc: "James Morris" <jmorris@namei.org>,
"Hervé Guillemet" <herve@guillemet.org>,
"Andrew G. Morgan" <morgan@kernel.org>,
"Casey Schaufler" <casey@schaufler-ca.com>
Subject: [PATCH] fix namespaced fscaps when !CONFIG_SECURITY
Date: Tue, 17 Nov 2020 09:08:56 -0600 [thread overview]
Message-ID: <20201117150856.GA12240@mail.hallyn.com> (raw)
Namespaced file capabilities were introduced in 8db6c34f1dbc .
When userspace reads an xattr for a namespaced capability, a
virtualized representation of it is returned if the caller is
in a user namespace owned by the capability's owning rootid.
The function which performs this virtualization was not hooked
up if CONFIG_SECURITY=n. Therefore in that case the original
xattr was shown instead of the virtualized one.
To test this using libcap-bin (*1),
$ v=$(mktemp)
$ unshare -Ur setcap cap_sys_admin-eip $v
$ unshare -Ur setcap -v cap_sys_admin-eip $v
/tmp/tmp.lSiIFRvt8Y: OK
"setcap -v" verifies the values instead of setting them, and
will check whether the rootid value is set. Therefore, with
this bug un-fixed, and with CONFIG_SECURITY=n, setcap -v will
fail:
$ v=$(mktemp)
$ unshare -Ur setcap cap_sys_admin=eip $v
$ unshare -Ur setcap -v cap_sys_admin=eip $v
nsowner[got=1000, want=0],/tmp/tmp.HHDiOOl9fY differs in []
Fix this bug by calling cap_inode_getsecurity() in
security_inode_getsecurity() instead of returning
-EOPNOTSUPP, when CONFIG_SECURITY=n.
*1 - note, if libcap is too old for getcap to have the '-n'
option, then use verify-caps instead.
Signed-off-by: Serge Hallyn <serge@hallyn.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1593431
Cc: Hervé Guillemet <herve@guillemet.org>
Cc: Andrew G. Morgan <morgan@kernel.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
---
include/linux/security.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index bc2725491560..39642626a707 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -869,7 +869,7 @@ static inline int security_inode_killpriv(struct dentry *dentry)
static inline int security_inode_getsecurity(struct inode *inode, const char *name, void **buffer, bool alloc)
{
- return -EOPNOTSUPP;
+ return cap_inode_getsecurity(inode, name, buffer, alloc);
}
static inline int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags)
--
2.25.1
next reply other threads:[~2020-11-17 15:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 15:08 Serge E. Hallyn [this message]
2020-11-17 16:11 ` [PATCH] fix namespaced fscaps when !CONFIG_SECURITY Andrew G. Morgan
2020-11-20 3:19 ` James Morris
2020-11-20 5:03 ` Andrew G. Morgan
2020-11-17 17:51 ` Casey Schaufler
2020-11-20 3:16 ` James Morris
2020-11-20 3:19 ` James Morris
[not found] ` <CALQRfL6q8ppuWi3ygY6iqh6SX9pnkVnvJDynTD61K2wUqerahg@mail.gmail.com>
2020-11-29 21:15 ` Serge E. Hallyn
2020-12-01 2:58 ` James Morris
2020-12-04 15:58 ` Andrew G. Morgan
2020-12-05 0:27 ` James Morris
2020-12-05 17:40 ` Serge E. Hallyn
2020-12-05 17:41 ` Serge E. Hallyn
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