From 0965232035cfa59a64d197cf8a8ee0bc407bb3e4 Mon Sep 17 00:00:00 2001
From: Alexey Dobriyan <adobriyan@gmail.com>
Date: Tue, 10 Apr 2018 16:34:45 -0700
Subject: [PATCH] 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            | 12 ++++++++++--
 include/linux/seq_file.h |  1 +
 init/main.c              |  1 +
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 0677e89f3c6f..3cb340583074 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);
+}
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 23d6a92cea9f..a121982af0f5 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -240,4 +240,5 @@ extern struct hlist_node *seq_hlist_start_percpu(struct hlist_head __percpu *hea
 
 extern struct hlist_node *seq_hlist_next_percpu(void *v, struct hlist_head __percpu *head, int *cpu, loff_t *pos);
 
+void seq_file_init(void);
 #endif
diff --git a/init/main.c b/init/main.c
index 50359a3162d0..b795aa341a3a 100644
--- a/init/main.c
+++ b/init/main.c
@@ -715,6 +715,7 @@ asmlinkage __visible void __init start_kernel(void)
 	vfs_caches_init();
 	pagecache_init();
 	signals_init();
+	seq_file_init();
 	proc_root_init();
 	nsfs_init();
 	cpuset_init();
-- 
2.34.1