commit 0965232035cfa59a64d197cf8a8ee0bc407bb3e4
author Alexey Dobriyan <adobriyan@gmail.com> Tue Apr 10 16:34:45 2018 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Wed Apr 11 10:28:36 2018 -0700
tree f6c65bb356de0d962666185d7d4435b9afe76861
parent 9ad553abe66f8be3f4755e9fa0a6ba137ce76341

seq_file: allocate seq_file from kmem_cache

For fine-grained debugging and usercopy protection.

Link: http://lkml.kernel.org/r/20180310085027.GA17121@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Glauber Costa <glommer@gmail.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/seq_file.c

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 0677e89..3cb3405 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -6,6 +6,7 @@
  * initial implementation -- AV, Oct 2001.
  */
 
+#include <linux/cache.h>
 #include <linux/fs.h>
 #include <linux/export.h>
 #include <linux/seq_file.h>
@@ -19,6 +20,8 @@
 #include <linux/uaccess.h>
 #include <asm/page.h>
 
+static struct kmem_cache *seq_file_cache __ro_after_init;
+
 static void seq_set_overflow(struct seq_file *m)
 {
 	m->count = m->size;
@@ -51,7 +54,7 @@ int seq_open(struct file *file, const struct seq_operations *op)
 
 	WARN_ON(file->private_data);
 
-	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	p = kmem_cache_zalloc(seq_file_cache, GFP_KERNEL);
 	if (!p)
 		return -ENOMEM;
 
@@ -366,7 +369,7 @@ int seq_release(struct inode *inode, struct file *file)
 {
 	struct seq_file *m = file->private_data;
 	kvfree(m->buf);
-	kfree(m);
+	kmem_cache_free(seq_file_cache, m);
 	return 0;
 }
 EXPORT_SYMBOL(seq_release);
@@ -1106,3 +1109,8 @@ seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head,
 	return NULL;
 }
 EXPORT_SYMBOL(seq_hlist_next_percpu);
+
+void __init seq_file_init(void)
+{
+	seq_file_cache = KMEM_CACHE(seq_file, SLAB_PANIC);
+}