Patch "kcov: detect double association with a single task" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    kcov: detect double association with a single task

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kcov-detect-double-association-with-a-single-task.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From a77660d231f8b3d84fd23ed482e0964f7aa546d6 Mon Sep 17 00:00:00 2001
From: Dmitry Vyukov <dvyukov@google.com>
Date: Tue, 6 Feb 2018 15:40:28 -0800
Subject: kcov: detect double association with a single task

From: Dmitry Vyukov <dvyukov@google.com>

commit a77660d231f8b3d84fd23ed482e0964f7aa546d6 upstream.

Currently KCOV_ENABLE does not check if the current task is already
associated with another kcov descriptor.  As the result it is possible
to associate a single task with more than one kcov descriptor, which
later leads to a memory leak of the old descriptor.  This relation is
really meant to be one-to-one (task has only one back link).

Extend validation to detect such misuse.

Link: http://lkml.kernel.org/r/20180122082520.15716-1-dvyukov@google.com
Fixes: 5c9a8750a640 ("kernel: add kcov code coverage")
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: Shankara Pailoor <sp3485@columbia.edu>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: syzbot <syzkaller@googlegroups.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/kcov.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -220,9 +220,9 @@ static int kcov_ioctl_locked(struct kcov
 		if (unused != 0 || kcov->mode == KCOV_MODE_DISABLED ||
 		    kcov->area == NULL)
 			return -EINVAL;
-		if (kcov->t != NULL)
-			return -EBUSY;
 		t = current;
+		if (kcov->t != NULL || t->kcov != NULL)
+			return -EBUSY;
 		/* Cache in task struct for performance. */
 		t->kcov_size = kcov->size;
 		t->kcov_area = kcov->area;


Patches currently in stable-queue which might be from dvyukov@google.com are

queue-4.9/kvm-x86-fix-escape-of-guest-dr6-to-the-host.patch
queue-4.9/blktrace-fix-unlocked-registration-of-tracepoints.patch
queue-4.9/netfilter-x_tables-fix-int-overflow-in-xt_alloc_table_info.patch
queue-4.9/netfilter-ipt_clusterip-fix-out-of-bounds-accesses-in-clusterip_tg_check.patch
queue-4.9/kcov-detect-double-association-with-a-single-task.patch