Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1620546

[PATCH 4.4 13/32] ptrace: fix PTRACE_LISTEN race corrupting task->state

Show all headers | View raw

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: bsegall@google.com <bsegall@google.com>

commit 5402e97af667e35e54177af8f6575518bf251d51 upstream.

In PT_SEIZED + LISTEN mode STOP/CONT signals cause a wakeup against
__TASK_TRACED.  If this races with the ptrace_unfreeze_traced at the end
of a PTRACE_LISTEN, this can wake the task /after/ the check against
__TASK_TRACED, but before the reset of state to TASK_TRACED.  This
causes it to instead clobber TASK_WAKING, allowing a subsequent wakeup
against TRACED while the task is still on the rq wake_list, corrupting
it.

Oleg said:
 "The kernel can crash or this can lead to other hard-to-debug problems.
  In short, "task->state = TASK_TRACED" in ptrace_unfreeze_traced()
  assumes that nobody else can wake it up, but PTRACE_LISTEN breaks the
  contract. Obviusly it is very wrong to manipulate task->state if this
  task is already running, or WAKING, or it sleeps again"

[akpm@linux-foundation.org: coding-style fixes]
Fixes: 9899d11f ("ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL")
Link: http://lkml.kernel.org/r/xm26y3vfhmkp.fsf_-_@bsegall-linux.mtv.corp.google.com
Signed-off-by: Ben Segall <bsegall@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/ptrace.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -151,11 +151,17 @@ static void ptrace_unfreeze_traced(struc
 
 	WARN_ON(!task->ptrace || task->parent != current);
 
+	/*
+	 * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely.
+	 * Recheck state under the lock to close this race.
+	 */
 	spin_lock_irq(&task->sighand->siglock);
-	if (__fatal_signal_pending(task))
-		wake_up_state(task, __TASK_TRACED);
-	else
-		task->state = TASK_TRACED;
+	if (task->state == __TASK_TRACED) {
+		if (__fatal_signal_pending(task))
+			wake_up_state(task, __TASK_TRACED);
+		else
+			task->state = TASK_TRACED;
+	}
 	spin_unlock_irq(&task->sighand->siglock);
 }
 

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH 4.4 00/32] 4.4.61-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 05/32] drm/vmwgfx: Remove getparam error message Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 01/32] drm/vmwgfx: Type-check lookups of fence objects Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 06/32] drm/vmwgfx: fix integer overflow in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:40 +0200
  [PATCH 4.4 28/32] MIPS: ralink: Fix typos in rt3883 pinctrl Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 09/32] arm/arm64: KVM: Take mmap_sem in stage2_unmap_vm Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 16/32] metag/usercopy: Fix alignment error checking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 30/32] MIPS: Lantiq: fix missing xbar kernel panic Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 32/32] mm/mempolicy.c: fix error handling in set_mempolicy and mbind. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 23/32] powerpc: Dont try to fix up misaligned load-with-reservation instructions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 20/32] metag/usercopy: Fix src fixup in from user rapf loops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 08/32] staging: android: ashmem: lseek failed due to no FMODE_LSEEK. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 29/32] MIPS: End spinlocks with .insn Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6 kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
    Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels "Maciej W. Rozycki" <macro@linux-mips.org> - 2017-04-15 01:50 +0200
      Re: [PATCH 4.4 27/32] MIPS: Force o32 fp64 support on 32bit MIPS64r6  kernels Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-19 15:20 +0200
  [PATCH 4.4 26/32] s390/uaccess: get_user() should zero on failure (again) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 31/32] MIPS: Flush wrong invalid FTLB entry for huge page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 14/32] ring-buffer: Fix return value check in test_ringbuffer() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 17/32] metag/usercopy: Add early abort to copy_to_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 22/32] powerpc/mm: Add missing global TLB invalidate if cxl is active Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 04/32] drm/ttm, drm/vmwgfx: Relax permission checking when opening surfaces Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 25/32] s390/decompressor: fix initrd corruption caused by bss clear Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 15/32] metag/usercopy: Drop unused macros Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 24/32] nios2: reserve boot memory for device tree Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 18:50 +0200
  [PATCH 4.4 21/32] metag/usercopy: Add missing fixups Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 11/32] iio: bmg160: reset chip when probing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 19/32] metag/usercopy: Set flags before ADDZ Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 13/32] ptrace: fix PTRACE_LISTEN race corrupting task->state Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 18/32] metag/usercopy: Zero rest of buffer from copy_from_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 10/32] arm/arm64: KVM: Take mmap_sem in kvm_arch_prepare_memory_region Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 12/32] Reset TreeId to zero on SMB2 TREE_CONNECT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 02/32] drm/vmwgfx: NULL pointer dereference in vmw_surface_define_ioctl() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  [PATCH 4.4 07/32] sysfs: be careful of error returns from ops->show() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-04-10 20:00 +0200
  Re: [PATCH 4.4 00/32] 4.4.61-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-04-10 22:40 +0200

csiph-web