[RFC PATCH 2/2] bust_spinlocks: do not decrement oops_in_progress unconditionally

["Paoloni, Gabriele" <gabriele.paoloni@intel.com>]

In the current implementation if the input flag is 0
oops_in_progress is unconditionally decremented, thus allowing
to become a negative number. Since right now oops_in_progress
is a global variable used in the kernel as a conditional flag
to check if oops, panic(), BUG() or die() is in progress the
current unconditional decrement may lead to unexpected behavior
in the Kernel paths conditionally executing over this flag.

This patch only decrement oops_in_progress if it is non zero

Signed-off-by: Gabriele Paoloni <gabriele.paoloni@intel.com>
---
 lib/bust_spinlocks.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/bust_spinlocks.c b/lib/bust_spinlocks.c
index 594b270161d9..842633ac9130 100644
--- a/lib/bust_spinlocks.c
+++ b/lib/bust_spinlocks.c
@@ -23,6 +23,9 @@
  * @yes: input flag; if zero decreases oops_in_progress,
  * otherwise increases it.
  *
+ * Note: if oops_in_progress is already 0 it will not
+ * be decreased
+ *
  */
 void bust_spinlocks(int yes)
 {
@@ -33,7 +36,9 @@ void bust_spinlocks(int yes)
 		unblank_screen();
 #endif
 		console_unblank();
-		if (--oops_in_progress == 0)
+		if (oops_in_progress)
+			oops_in_progress--;
+		if (!oops_in_progress)
 			wake_up_klogd();
 	}
 }
-- 
2.25.1

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