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-rw-r--r--lib/idr.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/lib/idr.c b/lib/idr.c
index 1a30272066c..73f4d53c02f 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -569,6 +569,7 @@ void idr_remove(struct idr *idp, int id)
struct idr_layer *p;
struct idr_layer *to_free;
+ /* see comment in idr_find_slowpath() */
if (WARN_ON_ONCE(id < 0))
return;
@@ -666,6 +667,14 @@ void *idr_find_slowpath(struct idr *idp, int id)
int n;
struct idr_layer *p;
+ /*
+ * If @id is negative, idr_find() used to ignore the sign bit and
+ * performed lookup with the rest of bits, which is weird and can
+ * lead to very obscure bugs. We're now returning NULL for all
+ * negative IDs but just in case somebody was depending on the sign
+ * bit being ignored, let's trigger WARN_ON_ONCE() so that they can
+ * be detected and fixed. WARN_ON_ONCE() can later be removed.
+ */
if (WARN_ON_ONCE(id < 0))
return NULL;
@@ -815,6 +824,7 @@ void *idr_replace(struct idr *idp, void *ptr, int id)
int n;
struct idr_layer *p, *old_p;
+ /* see comment in idr_find_slowpath() */
if (WARN_ON_ONCE(id < 0))
return ERR_PTR(-EINVAL);