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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: 5c9a8750a6 ("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>
This commit is contained in:
Dmitry Vyukov 2018-02-06 15:40:28 -08:00 committed by Linus Torvalds
parent a1be1f3931
commit a77660d231
1 changed files with 2 additions and 2 deletions
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4
kernel/kcov.c
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@ -358,7 +358,8 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
*/ */
if (kcov->mode != KCOV_MODE_INIT || !kcov->area) if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
return -EINVAL; return -EINVAL;
if (kcov->t != NULL) t = current;
if (kcov->t != NULL || t->kcov != NULL)
return -EBUSY; return -EBUSY;
if (arg == KCOV_TRACE_PC) if (arg == KCOV_TRACE_PC)
kcov->mode = KCOV_MODE_TRACE_PC; kcov->mode = KCOV_MODE_TRACE_PC;
@ -370,7 +371,6 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
#endif #endif
else else
return -EINVAL; return -EINVAL;
t = current;
/* Cache in task struct for performance. */ /* Cache in task struct for performance. */
t->kcov_size = kcov->size; t->kcov_size = kcov->size;
t->kcov_area = kcov->area; t->kcov_area = kcov->area;