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Commit a77660d2 authored by Dmitry Vyukov's avatar Dmitry Vyukov Committed by Linus Torvalds
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kcov: detect double association with a single task 

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: 5c9a8750 ("kernel: add kcov code coverage")
Signed-off-by: default avatarDmitry Vyukov <dvyukov@google.com>
Reported-by: default avatarShankara Pailoor <sp3485@columbia.edu>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: syzbot <syzkaller@googlegroups.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a1be1f39

kernel/kcov.c

+2 −2
Original line number Diff line number Diff line
@@ -358,7 +358,8 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, 
		 */

		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 *kcov, unsigned int cmd, 
#endif

		else

			return -EINVAL;

		t = current;

		/* Cache in task struct for performance. */

		t->kcov_size = kcov->size;

		t->kcov_area = kcov->area;