linux-kernel - [PATCH 3.16 177/306] s390/hypfs: Use get_free_page() instead of kmalloc to ensure page alignment

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Date:   Wed, 15 Feb 2017 22:41:40 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Martin Schwidefsky" <schwidefsky@...ibm.com>,
        "Michael Holzheu" <holzheu@...ux.vnet.ibm.com>
Subject: [PATCH 3.16 177/306] s390/hypfs: Use get_free_page() instead of
 kmalloc to ensure page alignment

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michael Holzheu <holzheu@...ux.vnet.ibm.com>

commit 237d6e6884136923b6bd26d5141ebe1d065960c9 upstream.

Since commit d86bd1bece6f ("mm/slub: support left redzone") it is no longer
guaranteed that kmalloc(PAGE_SIZE) returns page aligned memory.

After the above commit we get an error for diag224 because aligned
memory is required. This leads to the following user visible error:

 # mount none -t s390_hypfs /sys/hypervisor/
 mount: unknown filesystem type 's390_hypfs'

 # dmesg | grep hypfs
 hypfs.cccfb8: The hardware system does not provide all functions
               required by hypfs
 hypfs.7a79f0: Initialization of hypfs failed with rc=-61

Fix this problem and use get_free_page() instead of kmalloc() to get
correctly aligned memory.

Signed-off-by: Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/s390/hypfs/hypfs_diag.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/arch/s390/hypfs/hypfs_diag.c
+++ b/arch/s390/hypfs/hypfs_diag.c
@@ -517,11 +517,11 @@ static int diag224(void *ptr)
 static int diag224_get_name_table(void)
 {
 	/* memory must be below 2GB */
-	diag224_cpu_names = kmalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
+	diag224_cpu_names = (char *) __get_free_page(GFP_KERNEL | GFP_DMA);
 	if (!diag224_cpu_names)
 		return -ENOMEM;
 	if (diag224(diag224_cpu_names)) {
-		kfree(diag224_cpu_names);
+		free_page((unsigned long) diag224_cpu_names);
 		return -EOPNOTSUPP;
 	}
 	EBCASC(diag224_cpu_names + 16, (*diag224_cpu_names + 1) * 16);
@@ -530,7 +530,7 @@ static int diag224_get_name_table(void)
 
 static void diag224_delete_name_table(void)
 {
-	kfree(diag224_cpu_names);
+	free_page((unsigned long) diag224_cpu_names);
 }
 
 static int diag224_idx2name(int index, char *name)