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| author | Dan Carpenter <dan.carpenter@oracle.com> | 2022-01-28 22:57:01 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-02-05 12:38:59 +0100 |
| commit | 60765e43e40fbf7a1df828116172440510fcc3e4 (patch) | |
| tree | 4c5155689d85fde3f629702540b7aa38c3046e16 | |
| parent | db6fd92316a254be2097556f01bccecf560e53ce (diff) | |
| download | linux-stable-60765e43e40fbf7a1df828116172440510fcc3e4.tar.gz linux-stable-60765e43e40fbf7a1df828116172440510fcc3e4.tar.bz2 linux-stable-60765e43e40fbf7a1df828116172440510fcc3e4.zip | |
fanotify: Fix stale file descriptor in copy_event_to_user()
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>
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 6facdf476255..84ec851211d9 100644 --- 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 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); @@ -621,6 +618,9 @@ 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: |