[PATCH 5.6 084/161] lib: fix bitmap_parse() on 64-bit big endian archs

[Greg Kroah-Hartman]

From: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>

commit 81c4f4d924d5d009b5ed785a3e22b18d0f7b831f upstream.

Commit 2d6261583be0 ("lib: rework bitmap_parse()") does not take into
account order of halfwords on 64-bit big endian architectures.  As
result (at least) Receive Packet Steering, IRQ affinity masks and
runtime kernel test "test_bitmap" get broken on s390.

[andriy.shevchenko@xxxxxxxxxxxxxxx: convert infinite while loop to a for loop]
  Link: http://lkml.kernel.org/r/20200609140535.87160-1-andriy.shevchenko@xxxxxxxxxxxxxxx

Fixes: 2d6261583be0 ("lib: rework bitmap_parse()")
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Cc: Amritha Nambiar <amritha.nambiar@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Cc: "Tobin C . Harding" <tobin@xxxxxxxxxx>
Cc: Vineet Gupta <vineet.gupta1@xxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1591634471-17647-1-git-send-email-agordeev@xxxxxxxxxxxxx
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 lib/bitmap.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -740,8 +740,9 @@ int bitmap_parse(const char *start, unsi
 	int chunks = BITS_TO_U32(nmaskbits);
 	u32 *bitmap = (u32 *)maskp;
 	int unset_bit;
+	int chunk;
 
-	while (1) {
+	for (chunk = 0; ; chunk++) {
 		end = bitmap_find_region_reverse(start, end);
 		if (start > end)
 			break;
@@ -749,7 +750,11 @@ int bitmap_parse(const char *start, unsi
 		if (!chunks--)
 			return -EOVERFLOW;
 
-		end = bitmap_get_x32_reverse(start, end, bitmap++);
+#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
+		end = bitmap_get_x32_reverse(start, end, &bitmap[chunk ^ 1]);
+#else
+		end = bitmap_get_x32_reverse(start, end, &bitmap[chunk]);
+#endif
 		if (IS_ERR(end))
 			return PTR_ERR(end);
 	}