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authorLinus Torvalds <torvalds@linux-foundation.org>2019-04-30 15:03:00 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-04-30 15:03:00 -0700
commitf2bc9c908dfe3f56fe4ca4d92e5c5be80963b973 (patch)
tree885ecc2c3e864ed4fe0a3b062ce4f72fa72958aa
parentbf3bd966dfd7d9582f50e9bd08b15922197cd277 (diff)
parentb1da6a51871c6929dced1a7fad81990988b36ed6 (diff)
Merge tag 'fsnotify_for_v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs
Pull fsnotify fix from Jan Kara: "A fix of user trigerable NULL pointer dereference syzbot has recently spotted. The problem was introduced in this merge window so no CC stable is needed" * tag 'fsnotify_for_v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs: fsnotify: Fix NULL ptr deref in fanotify_get_fsid()
-rw-r--r--fs/notify/fanotify/fanotify.c14
-rw-r--r--fs/notify/mark.c12
2 files changed, 18 insertions, 8 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 6b9c27548997..63c6bb1f8c4d 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -346,10 +346,16 @@ static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
__kernel_fsid_t fsid = {};
fsnotify_foreach_obj_type(type) {
+ struct fsnotify_mark_connector *conn;
+
if (!fsnotify_iter_should_report_type(iter_info, type))
continue;
- fsid = iter_info->marks[type]->connector->fsid;
+ conn = READ_ONCE(iter_info->marks[type]->connector);
+ /* Mark is just getting destroyed or created? */
+ if (!conn)
+ continue;
+ fsid = conn->fsid;
if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
continue;
return fsid;
@@ -408,8 +414,12 @@ static int fanotify_handle_event(struct fsnotify_group *group,
return 0;
}
- if (FAN_GROUP_FLAG(group, FAN_REPORT_FID))
+ if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
fsid = fanotify_get_fsid(iter_info);
+ /* Racing with mark destruction or creation? */
+ if (!fsid.val[0] && !fsid.val[1])
+ return 0;
+ }
event = fanotify_alloc_event(group, inode, mask, data, data_type,
&fsid);
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index d593d4269561..22acb0a79b53 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -239,13 +239,13 @@ static void fsnotify_drop_object(unsigned int type, void *objp)
void fsnotify_put_mark(struct fsnotify_mark *mark)
{
- struct fsnotify_mark_connector *conn;
+ struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
void *objp = NULL;
unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
bool free_conn = false;
/* Catch marks that were actually never attached to object */
- if (!mark->connector) {
+ if (!conn) {
if (refcount_dec_and_test(&mark->refcnt))
fsnotify_final_mark_destroy(mark);
return;
@@ -255,10 +255,9 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
* We have to be careful so that traversals of obj_list under lock can
* safely grab mark reference.
*/
- if (!refcount_dec_and_lock(&mark->refcnt, &mark->connector->lock))
+ if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
return;
- conn = mark->connector;
hlist_del_init_rcu(&mark->obj_list);
if (hlist_empty(&conn->list)) {
objp = fsnotify_detach_connector_from_object(conn, &type);
@@ -266,7 +265,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
} else {
__fsnotify_recalc_mask(conn);
}
- mark->connector = NULL;
+ WRITE_ONCE(mark->connector, NULL);
spin_unlock(&conn->lock);
fsnotify_drop_object(type, objp);
@@ -620,7 +619,7 @@ restart:
/* mark should be the last entry. last is the current last entry */
hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
added:
- mark->connector = conn;
+ WRITE_ONCE(mark->connector, conn);
out_err:
spin_unlock(&conn->lock);
spin_unlock(&mark->lock);
@@ -808,6 +807,7 @@ void fsnotify_init_mark(struct fsnotify_mark *mark,
refcount_set(&mark->refcnt, 1);
fsnotify_get_group(group);
mark->group = group;
+ WRITE_ONCE(mark->connector, NULL);
}
/*