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authorElena Reshetova <elena.reshetova@intel.com>2017-11-18 02:29:39 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-18 03:10:03 +0300
commitd4f0284a5969fd7809ec8df710eb10598b701638 (patch)
treea38d9b3bbf2722d859a374dbe2cf06a97fa13273 /fs/nilfs2/the_nilfs.h
parent31ccb1f7ba3cfe29631587d451cf5bb8ab593550 (diff)
downloadlinux-d4f0284a5969fd7809ec8df710eb10598b701638.tar.xz
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/the_nilfs.h')
-rw-r--r--fs/nilfs2/the_nilfs.h5
1 files changed, 3 insertions, 2 deletions
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)