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Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull core locking updates from Thomas Gleixner.

* 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Mark get_robust_list as deprecated
  futex: Do not leak robust list to unprivileged process
This commit is contained in:
Linus Torvalds 2012-03-30 18:07:13 -07:00
parent 623ff7739e ec0c4274e3
commit 3a0d184943
3 changed files with 42 additions and 48 deletions
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10
Documentation/feature-removal-schedule.txt
View File

@ -529,3 +529,13 @@ When: 3.5
Why: The old kmap_atomic() with two arguments is deprecated, we only
keep it for backward compatibility for few cycles and then drop it.
Who: Cong Wang <amwang@redhat.com>
----------------------------
What: get_robust_list syscall
When: 2013
Why: There appear to be no production users of the get_robust_list syscall,
and it runs the risk of leaking address locations, allowing the bypass
of ASLR. It was only ever intended for debugging, so it should be
removed.
Who: Kees Cook <keescook@chromium.org>

40
kernel/futex.c
View File

@ -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 +2444,31 @@ 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;
if (!pid)
head = current->robust_list;
else {
struct task_struct *p;
WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
ret = -ESRCH;
rcu_read_lock();
rcu_read_lock();
ret = -ESRCH;
if (!pid)
p = current;
else {
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);

40
kernel/futex_compat.c
View File

@ -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 +137,31 @@ 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;
if (!pid)
head = current->compat_robust_list;
else {
struct task_struct *p;
WARN_ONCE(1, "deprecated: get_robust_list will be deleted in 2013.\n");
ret = -ESRCH;
rcu_read_lock();
rcu_read_lock();
ret = -ESRCH;
if (!pid)
p = current;
else {
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);