From: Amir Goldstein amir73il@gmail.com
commit c285a2f01d692ef48d7243cf1072897bbd237407 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/notify/fanotify/fanotify.c | 4 ++++ fs/notify/mark.c | 14 +++++++++++--- include/linux/fsnotify_backend.h | 4 +++- 3 files changed, 18 insertions(+), 4 deletions(-)
--- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -355,6 +355,10 @@ static __kernel_fsid_t fanotify_get_fsid /* 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; --- a/fs/notify/mark.c +++ b/fs/notify/mark.c @@ -495,10 +495,13 @@ static int fsnotify_attach_connector_to_ 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)); /* @@ -573,7 +576,12 @@ 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])) { /* --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -292,7 +292,9 @@ typedef struct fsnotify_mark_connector _ */ 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] */