+ ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: ocfs2: Use zero-sized array and struct_size() in kzalloc()
has been added to the -mm tree.  Its filename is
     ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc.patch

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------------------------------------------------------
From: "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx>
Subject: ocfs2: Use zero-sized array and struct_size() in kzalloc()

Update the code to use a zero-sized array instead of a pointer in
structure ocfs2_slot_info and use struct_size() in kzalloc().

Notice that one of the more common cases of allocation size calculations is
finding the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Link: http://lkml.kernel.org/r/20190108191903.GA22056@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Mark Fasheh <mfasheh@xxxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Joseph Qi <joseph.qi@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---


--- a/fs/ocfs2/slot_map.c~ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc
+++ a/fs/ocfs2/slot_map.c
@@ -55,7 +55,7 @@ struct ocfs2_slot_info {
 	unsigned int si_blocks;
 	struct buffer_head **si_bh;
 	unsigned int si_num_slots;
-	struct ocfs2_slot *si_slots;
+	struct ocfs2_slot si_slots[];
 };
 
 
@@ -420,9 +420,7 @@ int ocfs2_init_slot_info(struct ocfs2_su
 	struct inode *inode = NULL;
 	struct ocfs2_slot_info *si;
 
-	si = kzalloc(sizeof(struct ocfs2_slot_info) +
-		     (sizeof(struct ocfs2_slot) * osb->max_slots),
-		     GFP_KERNEL);
+	si = kzalloc(struct_size(si, si_slots, osb->max_slots), GFP_KERNEL);
 	if (!si) {
 		status = -ENOMEM;
 		mlog_errno(status);
@@ -431,8 +429,6 @@ int ocfs2_init_slot_info(struct ocfs2_su
 
 	si->si_extended = ocfs2_uses_extended_slot_map(osb);
 	si->si_num_slots = osb->max_slots;
-	si->si_slots = (struct ocfs2_slot *)((char *)si +
-					     sizeof(struct ocfs2_slot_info));
 
 	inode = ocfs2_get_system_file_inode(osb, SLOT_MAP_SYSTEM_INODE,
 					    OCFS2_INVALID_SLOT);
_

Patches currently in -mm which might be from gustavo@xxxxxxxxxxxxxx are

ocfs2-use-zero-sized-array-and-struct_size-in-kzalloc.patch
mm-memcontrol-use-struct_size-in-kmalloc.patch
gcov-use-struct_size-in-kzalloc.patch