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authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 10:37:38 +0300
committerMike Snitzer <snitzer@redhat.com>2017-10-24 22:09:51 +0300
commit2a0b4682e09d76466f7b8f5e347ae2ff02f033af (patch)
tree1f54fee8c0178790f22468e64f8b2984ffe828de /drivers/md/dm-table.c
parentbb176f67090ca54869fc1262c913aa69d2ede070 (diff)
downloadlinux-2a0b4682e09d76466f7b8f5e347ae2ff02f033af.tar.xz
dm: convert dm_dev_internal.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 dm_dev_internal.count is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-table.c')
-rw-r--r--drivers/md/dm-table.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index ef7b8f201f73..fc7d240cbf05 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -451,15 +451,15 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
return r;
}
- atomic_set(&dd->count, 0);
+ refcount_set(&dd->count, 1);
list_add(&dd->list, &t->devices);
} else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
r = upgrade_mode(dd, mode, t->md);
if (r)
return r;
+ refcount_inc(&dd->count);
}
- atomic_inc(&dd->count);
*result = dd->dm_dev;
return 0;
@@ -515,7 +515,7 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d)
dm_device_name(ti->table->md), d->name);
return;
}
- if (atomic_dec_and_test(&dd->count)) {
+ if (refcount_dec_and_test(&dd->count)) {
dm_put_table_device(ti->table->md, d);
list_del(&dd->list);
kfree(dd);