fanotify: update connector fsid cache on add mark

When implementing connector fsid cache, we only initialized the cache
when the first mark added to object was added by FAN_REPORT_FID group.
We forgot to update conn->fsid when the second mark is added by
FAN_REPORT_FID group to an already attached connector without fsid
cache.

Reported-and-tested-by: syzbot+c277e8e2f46414645508@syzkaller.appspotmail.com
Fixes: 77115225acc6 ("fanotify: cache fsid in fsnotify_mark_connector")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index e6fde1a..b428c29 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -355,6 +355,10 @@ static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
                /* Mark is just getting destroyed or created? */
                if (!conn)
                        continue;
+               if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID))
+                       continue;
+               /* Pairs with smp_wmb() in fsnotify_add_mark_list() */
+               smp_rmb();
                fsid = conn->fsid;
                if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
                        continue;

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 25eb247..99ddd12 100644 (file)
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -482,10 +482,13 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
        conn->type = type;
        conn->obj = connp;
        /* Cache fsid of filesystem containing the object */
-       if (fsid)
+       if (fsid) {
                conn->fsid = *fsid;
-       else
+               conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
+       } else {
                conn->fsid.val[0] = conn->fsid.val[1] = 0;
+               conn->flags = 0;
+       }
        if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
                inode = igrab(fsnotify_conn_inode(conn));
        /*
@@ -560,7 +563,12 @@ restart:
                if (err)
                        return err;
                goto restart;
-       } else if (fsid && (conn->fsid.val[0] || conn->fsid.val[1]) &&
+       } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
+               conn->fsid = *fsid;
+               /* Pairs with smp_rmb() in fanotify_get_fsid() */
+               smp_wmb();
+               conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
+       } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
                   (fsid->val[0] != conn->fsid.val[0] ||
                    fsid->val[1] != conn->fsid.val[1])) {
                /*

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index a9f9dcc..d4844ca 100644 (file)
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -292,7 +292,9 @@ typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;
  */
 struct fsnotify_mark_connector {
        spinlock_t lock;
-       unsigned int type;      /* Type of object [lock] */
+       unsigned short type;    /* Type of object [lock] */
+#define FSNOTIFY_CONN_FLAG_HAS_FSID    0x01
+       unsigned short flags;   /* flags [lock] */
        __kernel_fsid_t fsid;   /* fsid of filesystem containing object */
        union {
                /* Object pointer [lock] */