Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.15 26/32] fanotify: Fix stale file descriptor in copy_event_to_user() | Date | Fri, 4 Feb 2022 10:22:36 +0100 |
| |
From: Dan Carpenter <dan.carpenter@oracle.com>
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> --- fs/notify/fanotify/fanotify_user.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -611,9 +611,6 @@ static ssize_t copy_event_to_user(struct if (fanotify_is_perm_event(event->mask)) FANOTIFY_PERM(event)->fd = fd; - if (f) - fd_install(fd, f); - if (info_mode) { ret = copy_info_records_to_user(event, info, info_mode, pidfd, buf, count); @@ -621,6 +618,9 @@ static ssize_t copy_event_to_user(struct goto out_close_fd; } + if (f) + fd_install(fd, f); + return metadata.event_len; out_close_fd:
| |