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5cd9c58fbe
Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags
the target process if that is not the current process and it is trying to
change its own flags in a different way at the same time.
__capable() is using neither atomic ops nor locking to protect t->flags. This
patch removes __capable() and introduces has_capability() that doesn't set
PF_SUPERPRIV on the process being queried.
This patch further splits security_ptrace() in two:
(1) security_ptrace_may_access(). This passes judgement on whether one
process may access another only (PTRACE_MODE_ATTACH for ptrace() and
PTRACE_MODE_READ for /proc), and takes a pointer to the child process.
current is the parent.
(2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only,
and takes only a pointer to the parent process. current is the child.
In Smack and commoncap, this uses has_capability() to determine whether
the parent will be permitted to use PTRACE_ATTACH if normal checks fail.
This does not set PF_SUPERPRIV.
Two of the instances of __capable() actually only act on current, and so have
been changed to calls to capable().
Of the places that were using __capable():
(1) The OOM killer calls __capable() thrice when weighing the killability of a
process. All of these now use has_capability().
(2) cap_ptrace() and smack_ptrace() were using __capable() to check to see
whether the parent was allowed to trace any process. As mentioned above,
these have been split. For PTRACE_ATTACH and /proc, capable() is now
used, and for PTRACE_TRACEME, has_capability() is used.
(3) cap_safe_nice() only ever saw current, so now uses capable().
(4) smack_setprocattr() rejected accesses to tasks other than current just
after calling __capable(), so the order of these two tests have been
switched and capable() is used instead.
(5) In smack_file_send_sigiotask(), we need to allow privileged processes to
receive SIGIO on files they're manipulating.
(6) In smack_task_wait(), we let a process wait for a privileged process,
whether or not the process doing the waiting is privileged.
I've tested this with the LTP SELinux and syscalls testscripts.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: James Morris <jmorris@namei.org>
106 lines
2.8 KiB
C
106 lines
2.8 KiB
C
/*
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* Root Plug sample LSM module
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*
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* Originally written for a Linux Journal.
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*
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* Copyright (C) 2002 Greg Kroah-Hartman <greg@kroah.com>
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*
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* Prevents any programs running with egid == 0 if a specific USB device
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* is not present in the system. Yes, it can be gotten around, but is a
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* nice starting point for people to play with, and learn the LSM
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* interface.
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*
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* If you want to turn this into something with a semblance of security,
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* you need to hook the task_* functions also.
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*
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* See http://www.linuxjournal.com/article.php?sid=6279 for more information
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* about this code.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/security.h>
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#include <linux/usb.h>
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#include <linux/moduleparam.h>
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/* default is a generic type of usb to serial converter */
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static int vendor_id = 0x0557;
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static int product_id = 0x2008;
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module_param(vendor_id, uint, 0400);
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module_param(product_id, uint, 0400);
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/* should we print out debug messages */
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static int debug = 0;
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module_param(debug, bool, 0600);
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#define MY_NAME "root_plug"
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#define root_dbg(fmt, arg...) \
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do { \
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if (debug) \
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printk(KERN_DEBUG "%s: %s: " fmt , \
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MY_NAME , __func__ , \
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## arg); \
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} while (0)
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static int rootplug_bprm_check_security (struct linux_binprm *bprm)
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{
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struct usb_device *dev;
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root_dbg("file %s, e_uid = %d, e_gid = %d\n",
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bprm->filename, bprm->e_uid, bprm->e_gid);
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if (bprm->e_gid == 0) {
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dev = usb_find_device(vendor_id, product_id);
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if (!dev) {
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root_dbg("e_gid = 0, and device not found, "
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"task not allowed to run...\n");
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return -EPERM;
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}
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usb_put_dev(dev);
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}
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return 0;
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}
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static struct security_operations rootplug_security_ops = {
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/* Use the capability functions for some of the hooks */
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.ptrace_may_access = cap_ptrace_may_access,
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.ptrace_traceme = cap_ptrace_traceme,
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.capget = cap_capget,
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.capset_check = cap_capset_check,
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.capset_set = cap_capset_set,
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.capable = cap_capable,
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.bprm_apply_creds = cap_bprm_apply_creds,
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.bprm_set_security = cap_bprm_set_security,
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.task_post_setuid = cap_task_post_setuid,
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.task_reparent_to_init = cap_task_reparent_to_init,
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.task_prctl = cap_task_prctl,
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.bprm_check_security = rootplug_bprm_check_security,
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};
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static int __init rootplug_init (void)
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{
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/* register ourselves with the security framework */
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if (register_security (&rootplug_security_ops)) {
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printk (KERN_INFO
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"Failure registering Root Plug module with the kernel\n");
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return -EINVAL;
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}
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printk (KERN_INFO "Root Plug module initialized, "
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"vendor_id = %4.4x, product id = %4.4x\n", vendor_id, product_id);
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return 0;
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}
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security_initcall (rootplug_init);
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