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>
---
fs/ocfs2/slot_map.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
--- 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);
_
