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;
struct boo entry[];
};
size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kmalloc(size, GFP_KERNEL);
Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:
instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);
Also, notice that variable size is unnecessary, hence it is removed.
This code was detected with the help of Coccinelle.
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
fs/select.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 6cbc9ff56ba0..2a179ab68c60 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -966,7 +966,7 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
struct timespec64 *end_time)
{
struct poll_wqueues table;
- int err = -EFAULT, fdcount, len, size;
+ int err = -EFAULT, fdcount, len;
/* Allocate small arguments on the stack to save memory and be
faster - use long to make sure the buffer is aligned properly
on 64 bit archs to avoid unaligned access */
@@ -994,8 +994,8 @@ static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
break;
len = min(todo, POLLFD_PER_PAGE);
- size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
- walk = walk->next = kmalloc(size, GFP_KERNEL);
+ walk = walk->next = kmalloc(struct_size(walk, entries, len),
+ GFP_KERNEL);
if (!walk) {
err = -ENOMEM;
goto out_fds;
--
2.21.0
