[PATCH 1/2] seq_file: allocate seq_file from kmem_cache

From: Alexey Dobriyan
Date: Sat Mar 10 2018 - 03:50:39 EST


For fine-grained debugging and usercopy protection.

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
---

fs/seq_file.c | 12 ++++++++++--
include/linux/seq_file.h | 1 +
init/main.c | 1 +
3 files changed, 12 insertions(+), 2 deletions(-)

--- 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);
+}
--- 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
--- a/init/main.c
+++ b/init/main.c
@@ -696,6 +696,7 @@ asmlinkage __visible void __init start_kernel(void)
vfs_caches_init();
pagecache_init();
signals_init();
+ seq_file_init();
proc_root_init();
nsfs_init();
cpuset_init();