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Merge tag 'fsnotify_for_v5.1-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

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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()
This commit is contained in:
Linus Torvalds 2019-04-30 15:03:00 -07:00
commit f2bc9c908d
2 changed files with 18 additions and 8 deletions
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14
fs/notify/fanotify/fanotify.c
View File

@ -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);

12
fs/notify/mark.c
View File

@ -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 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
/* 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);
}
/*