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| author | Dan Carpenter <dan.carpenter@oracle.com> | 2022-01-28 22:57:01 +0300 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2022-02-01 12:52:07 +0100 |
| commit | ee12595147ac1fbfb5bcb23837e26dd58d94b15d (patch) | |
| tree | 23b335c261ec5a532107c5c69fe95348bd57db83 /fs/notify | |
| parent | 26291c54e111ff6ba87a164d85d4a4e134b7315c (diff) | |
| download | linux-ee12595147ac1fbfb5bcb23837e26dd58d94b15d.tar.bz2 | |
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.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 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: |