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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 14:37:56 +0300 |
| commit | 7b4741644cf718c422187e74fb07661ef1d68e85 (patch) | |
| tree | b818d49045c0737b10c164ea4e071e8f82b0f97c /fs/notify | |
| parent | 4d3fcfe8464838b3920bc2b939d888e0b792934e (diff) | |
| download | linux-7b4741644cf718c422187e74fb07661ef1d68e85.tar.xz | |
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>
Diffstat (limited to 'fs/notify')
| -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 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: |