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kcov: detect double association with a single task

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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>
This commit is contained in:
Dmitry Vyukov 2018-02-06 15:40:28 -08:00 committed by Greg Kroah-Hartman
parent 7b5ec55059
commit 4249e8af81
1 changed files with 2 additions and 2 deletions
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4
kernel/kcov.c
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@ -225,9 +225,9 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
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;