linux-kernel - [PATCH RESEND2] lib: fix bitmap_parse() on 64-bit big endian archs

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Date:   Mon,  8 Jun 2020 12:23:49 +0200
From:   Alexander Gordeev <agordeev@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-s390@...r.kernel.org,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        "Tobin C . Harding" <tobin@...nel.org>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Will Deacon <will.deacon@....com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH RESEND2] lib: fix bitmap_parse() on 64-bit big endian archs

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.

Fixes: 2d6261583be0 ("lib: rework bitmap_parse()")
Cc: stable@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Yury Norov <yury.norov@...il.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Amritha Nambiar <amritha.nambiar@...el.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Kees Cook <keescook@...omium.org>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Miklos Szeredi <mszeredi@...hat.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Steffen Klassert <steffen.klassert@...unet.com>
Cc: "Tobin C . Harding" <tobin@...nel.org>
Cc: Vineet Gupta <vineet.gupta1@...opsys.com>
Cc: Will Deacon <will.deacon@....com>
Cc: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
 lib/bitmap.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 89260aa342d6..a725e4612984 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -717,6 +717,19 @@ static const char *bitmap_get_x32_reverse(const char *start,
 	return end;
 }
 
+#if defined(__BIG_ENDIAN) && defined(CONFIG_64BIT)
+static void save_x32_chunk(unsigned long *maskp, u32 chunk, int chunk_idx)
+{
+	maskp += (chunk_idx / 2);
+	((u32 *)maskp)[(chunk_idx & 1) ^ 1] = chunk;
+}
+#else
+static void save_x32_chunk(unsigned long *maskp, u32 chunk, int chunk_idx)
+{
+	((u32 *)maskp)[chunk_idx] = chunk;
+}
+#endif
+
 /**
  * bitmap_parse - convert an ASCII hex string into a bitmap.
  * @start: pointer to buffer containing string.
@@ -738,7 +751,8 @@ int bitmap_parse(const char *start, unsigned int buflen,
 {
 	const char *end = strnchrnul(start, buflen, '\n') - 1;
 	int chunks = BITS_TO_U32(nmaskbits);
-	u32 *bitmap = (u32 *)maskp;
+	int chunk_idx = 0;
+	u32 chunk;
 	int unset_bit;
 
 	while (1) {
@@ -749,9 +763,11 @@ int bitmap_parse(const char *start, unsigned int buflen,
 		if (!chunks--)
 			return -EOVERFLOW;
 
-		end = bitmap_get_x32_reverse(start, end, bitmap++);
+		end = bitmap_get_x32_reverse(start, end, &chunk);
 		if (IS_ERR(end))
 			return PTR_ERR(end);
+
+		save_x32_chunk(maskp, chunk, chunk_idx++);
 	}
 
 	unset_bit = (BITS_TO_U32(nmaskbits) - chunks) * 32;
-- 
2.23.0