[Drbd-dev] left shift of negative value in dcbp_set_pad_bits()

[David Butterfield]

This fixes a C undefined-behavior runtime error encountered by libubsan after gcc -fsanitize=undefined:
left shift of negative value in dcbp_set_pad_bits()

I mentioned this one before, but in the context of a boring compiler warning.
The runtime undefined-behavior may make it more interesting.


diff --git a/drbd/drbd_main.c b/drbd/drbd_main.c
index 062c5ca1..16b4f02d 100644
--- a/drbd/drbd_main.c
+++ b/drbd/drbd_main.c
@@ -1832,7 +1840,7 @@ static void dcbp_set_start(struct p_compressed_bm *p, int set)
 static void dcbp_set_pad_bits(struct p_compressed_bm *p, int n)
 {
	BUG_ON(n & ~0x7);
-	p->encoding = (p->encoding & (~0x7 << 4)) | (n << 4);
+	p->encoding = (p->encoding & (~0x7u << 4)) | (n << 4);
 }
 
 static int fill_bitmap_rle_bits(struct drbd_peer_device *peer_device,