diff options
| author | Elena Reshetova | 2017-11-17 15:29:39 -0800 |
|---|---|---|
| committer | Linus Torvalds | 2017-11-17 16:10:03 -0800 |
| commit | d4f0284a5969fd7809ec8df710eb10598b701638 (patch) | |
| tree | a38d9b3bbf2722d859a374dbe2cf06a97fa13273 /fs/nilfs2 | |
| parent | 31ccb1f7ba3cfe29631587d451cf5bb8ab593550 (diff) | |
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@lab.ntt.co.jp
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Suggested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: David Windsor <dwindsor@gmail.com>
Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2')
| -rw-r--r-- | fs/nilfs2/the_nilfs.c | 8 | ||||
| -rw-r--r-- | fs/nilfs2/the_nilfs.h | 5 |
2 files changed, 7 insertions, 6 deletions
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c index 2dd75bf619ad..afebb5067cec 100644 --- a/fs/nilfs2/the_nilfs.c +++ b/fs/nilfs2/the_nilfs.c @@ -737,7 +737,7 @@ struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno) } 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_nilfs *nilfs, __u64 cno) } 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_nilfs *nilfs, __u64 cno) 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_nilfs *nilfs, __u64 cno) 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 --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h index b305c6f033e7..883d732b0259 100644 --- a/fs/nilfs2/the_nilfs.h +++ b/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_nilfs *); 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) |