Commit 43e11fa2 authored Jul 16, 2019 by Gustavo A. R. Silva Committed by Linus Torvalds Jul 16, 2019

fs/select.c: use struct_size() in kmalloc()

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.

Link: http://lkml.kernel.org/r/20190604164226.GA13823@embeddedor


Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 79eb597c

fs/select.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -961,7 +961,7 @@ 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 */
		@@ -989,8 +989,8 @@ 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;

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