4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Vyukov <dvyukov@xxxxxxxxxx> 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@xxxxxxxxxx Fixes: 5c9a8750a640 ("kernel: add kcov code coverage") Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Reported-by: Shankara Pailoor <sp3485@xxxxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: syzbot <syzkaller@xxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/kcov.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -358,7 +358,8 @@ static int kcov_ioctl_locked(struct kcov */ if (kcov->mode != KCOV_MODE_INIT || !kcov->area) return -EINVAL; - if (kcov->t != NULL) + t = current; + if (kcov->t != NULL || t->kcov != NULL) return -EBUSY; if (arg == KCOV_TRACE_PC) kcov->mode = KCOV_MODE_TRACE_PC; @@ -370,7 +371,6 @@ static int kcov_ioctl_locked(struct kcov #endif else return -EINVAL; - t = current; /* Cache in task struct for performance. */ t->kcov_size = kcov->size; t->kcov_area = kcov->area;