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ceph: convert ceph_cap_snap.nref from atomic_t to refcount_t 

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Elena Reshetova 2017-03-03 11:15:07 +02:00 committed by Ilya Dryomov
parent 3997c01d26
commit 805692d0e0
3 changed files with 6 additions and 5 deletions
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4
fs/ceph/caps.c
View File

@ -1389,7 +1389,7 @@ static void __ceph_flush_snaps(struct ceph_inode_info *ci,
first_tid = cf->tid + 1;
capsnap = container_of(cf, struct ceph_cap_snap, cap_flush);
atomic_inc(&capsnap->nref);
refcount_inc(&capsnap->nref);
spin_unlock(&ci->i_ceph_lock);
dout("__flush_snaps %p capsnap %p tid %llu %s\n",
@ -2202,7 +2202,7 @@ static void __kick_flushing_caps(struct ceph_mds_client *mdsc,
inode, capsnap, cf->tid,
ceph_cap_string(capsnap->dirty));
atomic_inc(&capsnap->nref);
refcount_inc(&capsnap->nref);
spin_unlock(&ci->i_ceph_lock);
ret = __send_flush_snap(inode, session, capsnap, cap->mseq,

2
fs/ceph/snap.c
View File

@ -519,7 +519,7 @@ void ceph_queue_cap_snap(struct ceph_inode_info *ci)
capsnap->need_flush ? "" : "no_flush");
ihold(inode);
atomic_set(&capsnap->nref, 1);
refcount_set(&capsnap->nref, 1);
INIT_LIST_HEAD(&capsnap->ci_item);
capsnap->follows = old_snapc->seq;

5
fs/ceph/super.h
View File

@ -14,6 +14,7 @@
#include <linux/writeback.h>
#include <linux/slab.h>
#include <linux/posix_acl.h>
#include <linux/refcount.h>
#include <linux/ceph/libceph.h>
@ -162,7 +163,7 @@ struct ceph_cap_flush {
* data before flushing the snapped state (tracked here) back to the MDS.
*/
struct ceph_cap_snap {
atomic_t nref;
refcount_t nref;
struct list_head ci_item;
struct ceph_cap_flush cap_flush;
@ -191,7 +192,7 @@ struct ceph_cap_snap {
static inline void ceph_put_cap_snap(struct ceph_cap_snap *capsnap)
{
if (atomic_dec_and_test(&capsnap->nref)) {
if (refcount_dec_and_test(&capsnap->nref)) {
if (capsnap->xattr_blob)
ceph_buffer_put(capsnap->xattr_blob);
kfree(capsnap);