linux-toradex.git/include/linux/ptrace.h, branch v4.11-rc3

sched/headers: Prepare for new header dependencies before moving code to

2017-03-02T07:42:29+00:00

We are going to split  out of , which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder  file that just
maps to  to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

ptrace: Don't allow accessing an undumpable mm

2016-11-22T18:57:38+00:00

It is the reasonable expectation that if an executable file is not
readable there will be no way for a user without special privileges to
read the file.  This is enforced in ptrace_attach but if ptrace
is already attached before exec there is no enforcement for read-only
executables.

As the only way to read such an mm is through access_process_vm
spin a variant called ptrace_access_vm that will fail if the
target process is not being ptraced by the current process, or
the current process did not have sufficient privileges when ptracing
began to read the target processes mm.

In the ptrace implementations replace access_process_vm by
ptrace_access_vm.  There remain several ptrace sites that still use
access_process_vm as they are reading the target executables
instructions (for kernel consumption) or register stacks.  As such it
does not appear necessary to add a permission check to those calls.

This bug has always existed in Linux.

Fixes: v1.0
Cc: stable@vger.kernel.org
Reported-by: Andy Lutomirski 
Signed-off-by: "Eric W. Biederman"

ptrace: Capture the ptracer's creds not PT_PTRACE_CAP

2016-11-22T17:49:49+00:00

When the flag PT_PTRACE_CAP was added the PTRACE_TRACEME path was
overlooked.  This can result in incorrect behavior when an application
like strace traces an exec of a setuid executable.

Further PT_PTRACE_CAP does not have enough information for making good
security decisions as it does not report which user namespace the
capability is in.  This has already allowed one mistake through
insufficient granulariy.

I found this issue when I was testing another corner case of exec and
discovered that I could not get strace to set PT_PTRACE_CAP even when
running strace as root with a full set of caps.

This change fixes the above issue with strace allowing stracing as
root a setuid executable without disabling setuid.  More fundamentaly
this change allows what is allowable at all times, by using the correct
information in it's decision.

Cc: stable@vger.kernel.org
Fixes: 4214e42f96d4 ("v2.4.9.11 -> v2.4.9.12")
Signed-off-by: "Eric W. Biederman"

ptrace: use fsuid, fsgid, effective creds for fs access checks

2016-01-21T01:09:18+00:00

By checking the effective credentials instead of the real UID / permitted
capabilities, ensure that the calling process actually intended to use its
credentials.

To ensure that all ptrace checks use the correct caller credentials (e.g.
in case out-of-tree code or newly added code omits the PTRACE_MODE_*CREDS
flag), use two new flags and require one of them to be set.

The problem was that when a privileged task had temporarily dropped its
privileges, e.g.  by calling setreuid(0, user_uid), with the intent to
perform following syscalls with the credentials of a user, it still passed
ptrace access checks that the user would not be able to pass.

While an attacker should not be able to convince the privileged task to
perform a ptrace() syscall, this is a problem because the ptrace access
check is reused for things in procfs.

In particular, the following somewhat interesting procfs entries only rely
on ptrace access checks:

 /proc/$pid/stat - uses the check for determining whether pointers
     should be visible, useful for bypassing ASLR
 /proc/$pid/maps - also useful for bypassing ASLR
 /proc/$pid/cwd - useful for gaining access to restricted
     directories that contain files with lax permissions, e.g. in
     this scenario:
     lrwxrwxrwx root root /proc/13020/cwd -> /root/foobar
     drwx------ root root /root
     drwxr-xr-x root root /root/foobar
     -rw-r--r-- root root /root/foobar/secret

Therefore, on a system where a root-owned mode 6755 binary changes its
effective credentials as described and then dumps a user-specified file,
this could be used by an attacker to reveal the memory layout of root's
processes or reveal the contents of files he is not allowed to access
(through /proc/$pid/cwd).

[akpm@linux-foundation.org: fix warning]
Signed-off-by: Jann Horn 
Acked-by: Kees Cook 
Cc: Casey Schaufler 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Cc: James Morris 
Cc: "Serge E. Hallyn" 
Cc: Andy Shevchenko 
Cc: Andy Lutomirski 
Cc: Al Viro 
Cc: "Eric W. Biederman" 
Cc: Willy Tarreau 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

seccomp: add ptrace options for suspend/resume

2015-07-15T18:52:52+00:00

This patch is the first step in enabling checkpoint/restore of processes
with seccomp enabled.

One of the things CRIU does while dumping tasks is inject code into them
via ptrace to collect information that is only available to the process
itself. However, if we are in a seccomp mode where these processes are
prohibited from making these syscalls, then what CRIU does kills the task.

This patch adds a new ptrace option, PTRACE_O_SUSPEND_SECCOMP, that enables
a task from the init user namespace which has CAP_SYS_ADMIN and no seccomp
filters to disable (and re-enable) seccomp filters for another task so that
they can be successfully dumped (and restored). We restrict the set of
processes that can disable seccomp through ptrace because although today
ptrace can be used to bypass seccomp, there is some discussion of closing
this loophole in the future and we would like this patch to not depend on
that behavior and be future proofed for when it is removed.

Note that seccomp can be suspended before any filters are actually
installed; this behavior is useful on criu restore, so that we can suspend
seccomp, restore the filters, unmap our restore code from the restored
process' address space, and then resume the task by detaching and have the
filters resumed as well.

v2 changes:

* require that the tracer have no seccomp filters installed
* drop TIF_NOTSC manipulation from the patch
* change from ptrace command to a ptrace option and use this ptrace option
  as the flag to check. This means that as soon as the tracer
  detaches/dies, seccomp is re-enabled and as a corrollary that one can not
  disable seccomp across PTRACE_ATTACHs.

v3 changes:

* get rid of various #ifdefs everywhere
* report more sensible errors when PTRACE_O_SUSPEND_SECCOMP is incorrectly
  used

v4 changes:

* get rid of may_suspend_seccomp() in favor of a capable() check in ptrace
  directly

v5 changes:

* check that seccomp is not enabled (or suspended) on the tracer

Signed-off-by: Tycho Andersen 
CC: Will Drewry 
CC: Roland McGrath 
CC: Pavel Emelyanov 
CC: Serge E. Hallyn 
Acked-by: Oleg Nesterov 
Acked-by: Andy Lutomirski 
[kees: access seccomp.mode through seccomp_mode() instead]
Signed-off-by: Kees Cook

exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()

2014-12-11T01:41:10+00:00

Now that forget_original_parent() uses ->ptrace_entry for EXIT_DEAD tasks,
we can simply pass "dead_children" list to exit_ptrace() and remove
another release_task() loop.  Plus this way we do not need to drop and
reacquire tasklist_lock.

Also shift the list_empty(ptraced) check, if we want this optimization it
makes sense to eliminate the function call altogether.

Signed-off-by: Oleg Nesterov 
Cc: Aaron Tomlin 
Cc: Alexey Dobriyan 
Cc: "Eric W. Biederman" ,
Cc: Sterling Alexander 
Cc: Peter Zijlstra 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace,x86: force IRET path after a ptrace_stop()

2014-07-04T00:27:23+00:00

The 'sysret' fastpath does not correctly restore even all regular
registers, much less any segment registers or reflags values.  That is
very much part of why it's faster than 'iret'.

Normally that isn't a problem, because the normal ptrace() interface
catches the process using the signal handler infrastructure, which
always returns with an iret.

However, some paths can get caught using ptrace_event() instead of the
signal path, and for those we need to make sure that we aren't going to
return to user space using 'sysret'.  Otherwise the modifications that
may have been done to the register set by the tracer wouldn't
necessarily take effect.

Fix it by forcing IRET path by setting TIF_NOTIFY_RESUME from
arch_ptrace_stop_needed() which is invoked from ptrace_stop().

Signed-off-by: Tejun Heo 
Reported-by: Andy Lutomirski 
Acked-by: Oleg Nesterov 
Suggested-by: Linus Torvalds 
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds

ptrace: fix fork event messages across pid namespaces

2014-06-06T23:08:11+00:00

When tracing a process in another pid namespace, it's important for fork
event messages to contain the child's pid as seen from the tracer's pid
namespace, not the parent's.  Otherwise, the tracer won't be able to
correlate the fork event with later SIGTRAP signals it receives from the
child.

We still risk a race condition if a ptracer from a different pid
namespace attaches after we compute the pid_t value.  However, sending a
bogus fork event message in this unlikely scenario is still a vast
improvement over the status quo where we always send bogus fork event
messages to debuggers in a different pid namespace than the forking
process.

Signed-off-by: Matthew Dempsky 
Acked-by: Oleg Nesterov 
Cc: Kees Cook 
Cc: Julien Tinnes 
Cc: Roland McGrath 
Cc: Jan Kratochvil 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: revert "Prepare to fix racy accesses on task breakpoints"

2013-07-09T17:33:26+00:00

This reverts commit bf26c018490c ("Prepare to fix racy accesses on task
breakpoints").

The patch was fine but we can no longer race with SIGKILL after commit
9899d11f6544 ("ptrace: ensure arch_ptrace/ptrace_request can never race
with SIGKILL"), the __TASK_TRACED tracee can't be woken up and
->ptrace_bps[] can't go away.

Now that ptrace_get_breakpoints/ptrace_put_breakpoints have no callers,
we can kill them and remove task->ptrace_bp_refcnt.

Signed-off-by: Oleg Nesterov 
Acked-by: Frederic Weisbecker 
Acked-by: Michael Neuling 
Cc: Benjamin Herrenschmidt 
Cc: Ingo Molnar 
Cc: Jan Kratochvil 
Cc: Paul Mackerras 
Cc: Paul Mundt 
Cc: Will Deacon 
Cc: Prasad 
Cc: Russell King 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ia64: kill thread_matches(), unexport ptrace_check_attach()

2013-01-20T20:26:05+00:00

The ia64 function "thread_matches()" has no users since commit
e868a55c2a8c ("[IA64] remove find_thread_for_addr()").  Remove it.

This allows us to make ptrace_check_attach() static to kernel/ptrace.c,
which is good since we'll need to change the semantics of it and fix up
all the callers.

Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds