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%3Ba=su...

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