linux-toradex.git/kernel/ptrace.c, branch v3.14.3

exec/ptrace: fix get_dumpable() incorrect tests

2013-11-13T03:09:33+00:00

The get_dumpable() return value is not boolean.  Most users of the
function actually want to be testing for non-SUID_DUMP_USER(1) rather than
SUID_DUMP_DISABLE(0).  The SUID_DUMP_ROOT(2) is also considered a
protected state.  Almost all places did this correctly, excepting the two
places fixed in this patch.

Wrong logic:
    if (dumpable == SUID_DUMP_DISABLE) { /* be protective */ }
        or
    if (dumpable == 0) { /* be protective */ }
        or
    if (!dumpable) { /* be protective */ }

Correct logic:
    if (dumpable != SUID_DUMP_USER) { /* be protective */ }
        or
    if (dumpable != 1) { /* be protective */ }

Without this patch, if the system had set the sysctl fs/suid_dumpable=2, a
user was able to ptrace attach to processes that had dropped privileges to
that user.  (This may have been partially mitigated if Yama was enabled.)

The macros have been moved into the file that declares get/set_dumpable(),
which means things like the ia64 code can see them too.

CVE-2013-2929

Reported-by: Vasily Kulikov 
Signed-off-by: Kees Cook 
Cc: "Luck, Tony" 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

__ptrace_may_access() should not deny sub-threads

2013-09-11T22:59:01+00:00

__ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task !=
current, this can can lead to surprising results.

For example, a sub-thread can't readlink("/proc/self/exe") if the
executable is not readable.  setup_new_exec()->would_dump() notices that
inode_permission(MAY_READ) fails and then it does
set_dumpable(suid_dumpable).  After that get_dumpable() fails.

(It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we
could add PTRACE_MODE_NODUMPABLE)

Change __ptrace_may_access() to use same_thread_group() instead of "task
== current".  Any security check is pointless when the tasks share the
same ->mm.

Signed-off-by: Mark Grondona 
Signed-off-by: Ben Woodard 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Revert "ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child)"

2013-08-06T20:16:32+00:00

This reverts commit fab840fc2d542fabcab903db8e03589a6702ba5f.

This commit even has the test-case to prove that the tracee
can be killed by SIGTRAP if the debugger does not remove the
breakpoints before PTRACE_DETACH.

However, this is exactly what wineserver deliberately does,
set_thread_context() calls PTRACE_ATTACH + PTRACE_DETACH just
for PTRACE_POKEUSER(DR*) in between.

So we should revert this fix and document that PTRACE_DETACH
should keep the breakpoints.

Reported-by: Felipe Contreras 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Linus Torvalds

ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child)

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

Change ptrace_detach() to call flush_ptrace_hw_breakpoint(child).  This
frees the slots for non-ptrace PERF_TYPE_BREAKPOINT users, and this
ensures that the tracee won't be killed by SIGTRAP triggered by the
active breakpoints.

Test-case:

	unsigned long encode_dr7(int drnum, int enable, unsigned int type, unsigned int len)
	{
		unsigned long dr7;

		dr7 = ((len | type) & 0xf)
			<< (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
		if (enable)
			dr7 |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));

		return dr7;
	}

	int write_dr(int pid, int dr, unsigned long val)
	{
		return ptrace(PTRACE_POKEUSER, pid,
				offsetof (struct user, u_debugreg[dr]),
				val);
	}

	void func(void)
	{
	}

	int main(void)
	{
		int pid, stat;
		unsigned long dr7;

		pid = fork();
		if (!pid) {
			assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0);
			kill(getpid(), SIGHUP);

			func();
			return 0x13;
		}

		assert(pid == waitpid(-1, &stat, 0));
		assert(WSTOPSIG(stat) == SIGHUP);

		assert(write_dr(pid, 0, (long)func) == 0);
		dr7 = encode_dr7(0, 1, DR_RW_EXECUTE, DR_LEN_1);
		assert(write_dr(pid, 7, dr7) == 0);

		assert(ptrace(PTRACE_DETACH, pid, 0,0) == 0);
		assert(pid == waitpid(-1, &stat, 0));
		assert(stat == 0x1300);

		return 0;
	}

Before this patch the child is killed after PTRACE_DETACH.

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

ptrace: add ability to get/set signal-blocked mask

2013-07-03T23:08:01+00:00

crtools uses a parasite code for dumping processes.  The parasite code is
injected into a process with help PTRACE_SEIZE.

Currently crtools blocks signals from a parasite code.  If a process has
pending signals, crtools wait while a process handles these signals.

This method is not suitable for stopped tasks.  A stopped task can have a
few pending signals, when we will try to execute a parasite code, we will
need to drop SIGSTOP, but all other signals must remain pending, because a
state of processes must not be changed during checkpointing.

This patch adds two ptrace commands to set/get signal-blocked mask.

I think gdb can use this commands too.

[akpm@linux-foundation.org: be consistent with brace layout]
Signed-off-by: Andrey Vagin 
Reviewed-by: Oleg Nesterov 
Cc: Roland McGrath 
Cc: Michael Kerrisk 
Cc: Pavel Emelyanov 
Cc: Cyrill Gorcunov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Fix: kernel/ptrace.c: ptrace_peek_siginfo() missing __put_user() validation

2013-06-29T18:29:08+00:00

This __put_user() could be used by unprivileged processes to write into
kernel memory.  The issue here is that even if copy_siginfo_to_user()
fails, the error code is not checked before __put_user() is executed.

Luckily, ptrace_peek_siginfo() has been added within the 3.10-rc cycle,
so it has not hit a stable release yet.

Signed-off-by: Mathieu Desnoyers 
Acked-by: Oleg Nesterov 
Cc: Andrey Vagin 
Cc: Roland McGrath 
Cc: Paul McKenney 
Cc: David Howells 
Cc: Dave Jones 
Cc: Pavel Emelyanov 
Cc: Pedro Alves 
Cc: Andrew Morton 
Signed-off-by: Linus Torvalds

aio: don't include aio.h in sched.h

2013-05-08T03:16:25+00:00

Faster kernel compiles by way of fewer unnecessary includes.

[akpm@linux-foundation.org: fix fallout]
[akpm@linux-foundation.org: fix build]
Signed-off-by: Kent Overstreet 
Cc: Zach Brown 
Cc: Felipe Balbi 
Cc: Greg Kroah-Hartman 
Cc: Mark Fasheh 
Cc: Joel Becker 
Cc: Rusty Russell 
Cc: Jens Axboe 
Cc: Asai Thambi S P 
Cc: Selvan Mani 
Cc: Sam Bradshaw 
Cc: Jeff Moyer 
Cc: Al Viro 
Cc: Benjamin LaHaise 
Reviewed-by: "Theodore Ts'o" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ptrace: add ability to retrieve signals without removing from a queue (v4)

2013-05-01T00:04:05+00:00

This patch adds a new ptrace request PTRACE_PEEKSIGINFO.

This request is used to retrieve information about pending signals
starting with the specified sequence number.  Siginfo_t structures are
copied from the child into the buffer starting at "data".

The argument "addr" is a pointer to struct ptrace_peeksiginfo_args.
struct ptrace_peeksiginfo_args {
	u64 off;	/* from which siginfo to start */
	u32 flags;
	s32 nr;		/* how may siginfos to take */
};

"nr" has type "s32", because ptrace() returns "long", which has 32 bits on
i386 and a negative values is used for errors.

Currently here is only one flag PTRACE_PEEKSIGINFO_SHARED for dumping
signals from process-wide queue.  If this flag is not set, signals are
read from a per-thread queue.

The request PTRACE_PEEKSIGINFO returns a number of dumped signals.  If a
signal with the specified sequence number doesn't exist, ptrace returns
zero.  The request returns an error, if no signal has been dumped.

Errors:
EINVAL - one or more specified flags are not supported or nr is negative
EFAULT - buf or addr is outside your accessible address space.

A result siginfo contains a kernel part of si_code which usually striped,
but it's required for queuing the same siginfo back during restore of
pending signals.

This functionality is required for checkpointing pending signals.  Pedro
Alves suggested using it in "gdb" to peek at pending signals.  gdb already
uses PTRACE_GETSIGINFO to get the siginfo for the signal which was already
dequeued.  This functionality allows gdb to look at the pending signals
which were not reported yet.

The prototype of this code was developed by Oleg Nesterov.

Signed-off-by: Andrew Vagin 
Cc: Roland McGrath 
Cc: Oleg Nesterov 
Cc: "Paul E. McKenney" 
Cc: David Howells 
Cc: Dave Jones 
Cc: "Michael Kerrisk (man-pages)" 
Cc: Pavel Emelyanov 
Cc: Linus Torvalds 
Cc: Pedro Alves 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

uprobes: Add exports for module use

2013-02-08T16:47:13+00:00

The original pull message for uprobes (commit 654443e2) noted:

  This tree includes uprobes support in 'perf probe' - but SystemTap
  (and other tools) can take advantage of user probe points as well.

In order to actually be usable in module-based tools like SystemTap, the
interface needs to be exported.  This patch first adds the obvious
exports for uprobe_register and uprobe_unregister.  Then it also adds
one for task_user_regset_view, which is necessary to get the correct
state of userspace registers.

Signed-off-by: Josh Stone 
Signed-off-by: Oleg Nesterov