From: Dan Carpenter <dan.carpenter@oracle.com> stable inclusion from stable-v5.10.97 commit 7b4741644cf718c422187e74fb07661ef1d68e85 bugzilla: https://gitee.com/openeuler/kernel/issues/I55O0O Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit ee12595147ac1fbfb5bcb23837e26dd58d94b15d upstream. This code calls fd_install() which gives the userspace access to the fd. Then if copy_info_records_to_user() fails it calls put_unused_fd(fd) but that will not release it and leads to a stale entry in the file descriptor table. Generally you can't trust the fd after a call to fd_install(). The fix is to delay the fd_install() until everything else has succeeded. Fortunately it requires CAP_SYS_ADMIN to reach this code so the security impact is less. Fixes: f644bc449b37 ("fanotify: fix copy_event_to_user() fid error clean up") Link: https://lore.kernel.org/r/20220128195656.GA26981@kili Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by: Mathias Krause <minipli@grsecurity.net> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yu Liao <liaoyu15@huawei.com> Reviewed-by: Wei Li <liwei391@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- fs/notify/fanotify/fanotify_user.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 086b6bacbad1..18e014fa0648 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -366,9 +366,6 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, if (fanotify_is_perm_event(event->mask)) FANOTIFY_PERM(event)->fd = fd; - if (f) - fd_install(fd, f); - /* Event info records order is: dir fid + name, child fid */ if (fanotify_event_dir_fh_len(event)) { info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME : @@ -432,6 +429,9 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, count -= ret; } + if (f) + fd_install(fd, f); + return metadata.event_len; out_close_fd: -- 2.20.1