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authorElena Reshetova <elena.reshetova@intel.com>2017-11-18 00:29:39 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-18 01:10:03 +0100
commitd4f0284a5969fd7809ec8df710eb10598b701638 (patch)
treea38d9b3bbf2722d859a374dbe2cf06a97fa13273 /fs/nilfs2/the_nilfs.c
parentnilfs2: fix race condition that causes file system corruption (diff)
downloadlinux-d4f0284a5969fd7809ec8df710eb10598b701638.tar.xz
linux-d4f0284a5969fd7809ec8df710eb10598b701638.zip
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.c')
-rw-r--r--fs/nilfs2/the_nilfs.c8
1 files changed, 4 insertions, 4 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);