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/[email protected] Fixes: 5c9a875 ("kernel: add kcov code coverage") Signed-off-by: Dmitry Vyukov <[email protected]> Reported-by: Shankara Pailoor <[email protected]> Cc: Dmitry Vyukov <[email protected]> Cc: syzbot <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
ashr · Feb 7, 2018 · a77660d · a77660d
1 parent a1be1f3
commit a77660d
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/kernel/kcov.c b/kernel/kcov.c
@@ -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;