| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <tip-bdbb776f882f5ad431aa1e694c69c1c3d6a4a5b8@git.kernel.org>
Date: Thu, 29 Mar 2012 02:55:12 -0700
From: tip-bot for Kees Cook <keescook@...omium.org>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
serge.hallyn@...onical.com, a.p.zijlstra@...llo.nl,
dvhart@...ux.intel.com, jkosina@...e.cz, ebiederm@...ssion.com,
keescook@...omium.org, dhowells@...hat.com, tglx@...utronix.de
Subject: [tip:core/locking] futex:
Do not leak robust list to unprivileged process
Commit-ID: bdbb776f882f5ad431aa1e694c69c1c3d6a4a5b8
Gitweb: http://git.kernel.org/tip/bdbb776f882f5ad431aa1e694c69c1c3d6a4a5b8
Author: Kees Cook <keescook@...omium.org>
AuthorDate: Mon, 19 Mar 2012 16:12:53 -0700
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 29 Mar 2012 11:37:17 +0200
futex: Do not leak robust list to unprivileged process
It was possible to extract the robust list head address from a setuid
process if it had used set_robust_list(), allowing an ASLR info leak. This
changes the permission checks to be the same as those used for similar
info that comes out of /proc.
Running a setuid program that uses robust futexes would have had:
cred->euid != pcred->euid
cred->euid == pcred->uid
so the old permissions check would allow it. I'm not aware of any setuid
programs that use robust futexes, so this is just a preventative measure.
(This patch is based on changes from grsecurity.)
Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: Darren Hart <dvhart@...ux.intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Serge E. Hallyn <serge.hallyn@...onical.com>
Cc: kernel-hardening@...ts.openwall.com
Cc: spender@...ecurity.net
Link: http://lkml.kernel.org/r/20120319231253.GA20893@www.outflux.net
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
kernel/futex.c | 36 +++++++++++++-----------------------
kernel/futex_compat.c | 36 +++++++++++++-----------------------
2 files changed, 26 insertions(+), 46 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 72efa1e..d701be5 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -59,6 +59,7 @@
#include <linux/magic.h>
#include <linux/pid.h>
#include <linux/nsproxy.h>
+#include <linux/ptrace.h>
#include <asm/futex.h>
@@ -2443,40 +2444,29 @@ SYSCALL_DEFINE3(get_robust_list, int, pid,
{
struct robust_list_head __user *head;
unsigned long ret;
- const struct cred *cred = current_cred(), *pcred;
+ struct task_struct *p;
if (!futex_cmpxchg_enabled)
return -ENOSYS;
+ rcu_read_lock();
+
+ ret = -ESRCH;
if (!pid)
- head = current->robust_list;
+ p = current;
else {
- struct task_struct *p;
-
- ret = -ESRCH;
- rcu_read_lock();
p = find_task_by_vpid(pid);
if (!p)
goto err_unlock;
- ret = -EPERM;
- pcred = __task_cred(p);
- /* If victim is in different user_ns, then uids are not
- comparable, so we must have CAP_SYS_PTRACE */
- if (cred->user->user_ns != pcred->user->user_ns) {
- if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
- goto err_unlock;
- goto ok;
- }
- /* If victim is in same user_ns, then uids are comparable */
- if (cred->euid != pcred->euid &&
- cred->euid != pcred->uid &&
- !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
- goto err_unlock;
-ok:
- head = p->robust_list;
- rcu_read_unlock();
}
+ ret = -EPERM;
+ if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ goto err_unlock;
+
+ head = p->robust_list;
+ rcu_read_unlock();
+
if (put_user(sizeof(*head), len_ptr))
return -EFAULT;
return put_user(head, head_ptr);
diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 5f9e689..a9642d5 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -10,6 +10,7 @@
#include <linux/compat.h>
#include <linux/nsproxy.h>
#include <linux/futex.h>
+#include <linux/ptrace.h>
#include <asm/uaccess.h>
@@ -136,40 +137,29 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
{
struct compat_robust_list_head __user *head;
unsigned long ret;
- const struct cred *cred = current_cred(), *pcred;
+ struct task_struct *p;
if (!futex_cmpxchg_enabled)
return -ENOSYS;
+ rcu_read_lock();
+
+ ret = -ESRCH;
if (!pid)
- head = current->compat_robust_list;
+ p = current;
else {
- struct task_struct *p;
-
- ret = -ESRCH;
- rcu_read_lock();
p = find_task_by_vpid(pid);
if (!p)
goto err_unlock;
- ret = -EPERM;
- pcred = __task_cred(p);
- /* If victim is in different user_ns, then uids are not
- comparable, so we must have CAP_SYS_PTRACE */
- if (cred->user->user_ns != pcred->user->user_ns) {
- if (!ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
- goto err_unlock;
- goto ok;
- }
- /* If victim is in same user_ns, then uids are comparable */
- if (cred->euid != pcred->euid &&
- cred->euid != pcred->uid &&
- !ns_capable(pcred->user->user_ns, CAP_SYS_PTRACE))
- goto err_unlock;
-ok:
- head = p->compat_robust_list;
- rcu_read_unlock();
}
+ ret = -EPERM;
+ if (!ptrace_may_access(p, PTRACE_MODE_READ))
+ goto err_unlock;
+
+ head = p->compat_robust_list;
+ rcu_read_unlock();
+
if (put_user(sizeof(*head), len_ptr))
return -EFAULT;
return put_user(ptr_to_compat(head), head_ptr);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists