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authorDan Carpenter <dan.carpenter@oracle.com>2022-01-28 22:57:01 +0300
committerJan Kara <jack@suse.cz>2022-02-01 14:52:07 +0300
commitee12595147ac1fbfb5bcb23837e26dd58d94b15d (patch)
tree23b335c261ec5a532107c5c69fe95348bd57db83 /fs/notify
parent26291c54e111ff6ba87a164d85d4a4e134b7315c (diff)
downloadlinux-ee12595147ac1fbfb5bcb23837e26dd58d94b15d.tar.xz
fanotify: Fix stale file descriptor in copy_event_to_user()
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>
Diffstat (limited to 'fs/notify')
-rw-r--r--fs/notify/fanotify/fanotify_user.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 1026f67b1d1e..2ff6bd85ba8f 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -701,9 +701,6 @@ 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);
-
if (info_mode) {
ret = copy_info_records_to_user(event, info, info_mode, pidfd,
buf, count);
@@ -711,6 +708,9 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
goto out_close_fd;
}
+ if (f)
+ fd_install(fd, f);
+
return metadata.event_len;
out_close_fd: