idr: Fix integer overflow in idr_for_each_entry

[ Upstream commit f6341c5af4e6e15041be39976d16deca789555fa ]

If there is an entry at INT_MAX then idr_for_each_entry() will increment
id after handling it.  This is undefined behaviour, and is caught by
UBSAN.  Adding 1U to id forces the operation to be carried out as an
unsigned addition which (when assigned to id) will result in INT_MIN.
Since there is never an entry stored at INT_MIN, idr_get_next() will
return NULL, ending the loop as expected.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 4ec8986e5dfb61c7f2fd47abd2563893bb4deaa0..ac6e946b6767bba3d6750fafb374e364af1191b8 100644 (file)
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -185,7 +185,7 @@ static inline void idr_preload_end(void)
  * is convenient for a "not found" value.
  */
 #define idr_for_each_entry(idr, entry, id)                     \
-       for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)
+       for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; id += 1U)
 
 /**
  * idr_for_each_entry_ul() - Iterate over an IDR's elements of a given type.