The patch titled
Subject: fs, nilfs: convert nilfs_root.count from atomic_t to refcount_t
has been added to the -mm tree. Its filename is
fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t.patch
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From: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Subject: fs, nilfs: convert nilfs_root.count from atomic_t to refcount_t
atomic_t variables are currently used to implement reference counters with
the following properties:
- counter is initialized to 1 using atomic_set()
- a resource is freed upon counter reaching zero
- once counter reaches zero, its further
increments aren't allowed
- counter schema uses basic atomic operations
(set, inc, inc_not_zero, dec_and_test, etc.)
Such atomic variables should be converted to a newly provided refcount_t
type and API that prevents accidental counter overflows and underflows.
This is important since overflows and underflows can lead to
use-after-free situation and be exploitable.
The variable nilfs_root.count is used as pure reference counter. Convert
it to refcount_t and fix up the operations.
Link: http://lkml.kernel.org/r/1509367935-3086-3-git-send-email-konishi.ryusuke@xxxxxxxxxxxxx
Signed-off-by: Elena Reshetova <elena.reshetova@xxxxxxxxx>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Reviewed-by: David Windsor <dwindsor@xxxxxxxxx>
Reviewed-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/the_nilfs.c | 8 ++++----
fs/nilfs2/the_nilfs.h | 5 +++--
2 files changed, 7 insertions(+), 6 deletions(-)
diff -puN fs/nilfs2/the_nilfs.c~fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t fs/nilfs2/the_nilfs.c
--- a/fs/nilfs2/the_nilfs.c~fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t
+++ a/fs/nilfs2/the_nilfs.c
@@ -737,7 +737,7 @@ struct nilfs_root *nilfs_lookup_root(str
} else if (cno > root->cno) {
n = n->rb_right;
} else {
- atomic_inc(&root->count);
+ refcount_inc(&root->count);
spin_unlock(&nilfs->ns_cptree_lock);
return root;
}
@@ -776,7 +776,7 @@ nilfs_find_or_create_root(struct the_nil
} else if (cno > root->cno) {
p = &(*p)->rb_right;
} else {
- atomic_inc(&root->count);
+ refcount_inc(&root->count);
spin_unlock(&nilfs->ns_cptree_lock);
kfree(new);
return root;
@@ -786,7 +786,7 @@ nilfs_find_or_create_root(struct the_nil
new->cno = cno;
new->ifile = NULL;
new->nilfs = nilfs;
- atomic_set(&new->count, 1);
+ refcount_set(&new->count, 1);
atomic64_set(&new->inodes_count, 0);
atomic64_set(&new->blocks_count, 0);
@@ -806,7 +806,7 @@ nilfs_find_or_create_root(struct the_nil
void nilfs_put_root(struct nilfs_root *root)
{
- if (atomic_dec_and_test(&root->count)) {
+ if (refcount_dec_and_test(&root->count)) {
struct the_nilfs *nilfs = root->nilfs;
nilfs_sysfs_delete_snapshot_group(root);
diff -puN fs/nilfs2/the_nilfs.h~fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t fs/nilfs2/the_nilfs.h
--- a/fs/nilfs2/the_nilfs.h~fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t
+++ a/fs/nilfs2/the_nilfs.h
@@ -27,6 +27,7 @@
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/slab.h>
+#include <linux/refcount.h>
struct nilfs_sc_info;
struct nilfs_sysfs_dev_subgroups;
@@ -246,7 +247,7 @@ struct nilfs_root {
__u64 cno;
struct rb_node rb_node;
- atomic_t count;
+ refcount_t count;
struct the_nilfs *nilfs;
struct inode *ifile;
@@ -299,7 +300,7 @@ void nilfs_swap_super_block(struct the_n
static inline void nilfs_get_root(struct nilfs_root *root)
{
- atomic_inc(&root->count);
+ refcount_inc(&root->count);
}
static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
_
Patches currently in -mm which might be from elena.reshetova@xxxxxxxxx are
fs-nilfs-convert-nilfs_rootcount-from-atomic_t-to-refcount_t.patch
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