| From 4aa68e07d845562561f5e73c04aa521376e95252 Mon Sep 17 00:00:00 2001 |
| From: Eric Biggers <ebiggers@google.com> |
| Date: Mon, 18 Sep 2017 11:38:29 -0700 |
| Subject: KEYS: restrict /proc/keys by credentials at open time |
| |
| From: Eric Biggers <ebiggers@google.com> |
| |
| commit 4aa68e07d845562561f5e73c04aa521376e95252 upstream. |
| |
| When checking for permission to view keys whilst reading from |
| /proc/keys, we should use the credentials with which the /proc/keys file |
| was opened. This is because, in a classic type of exploit, it can be |
| possible to bypass checks for the *current* credentials by passing the |
| file descriptor to a suid program. |
| |
| Following commit 34dbbcdbf633 ("Make file credentials available to the |
| seqfile interfaces") we can finally fix it. So let's do it. |
| |
| Signed-off-by: Eric Biggers <ebiggers@google.com> |
| Signed-off-by: David Howells <dhowells@redhat.com> |
| Signed-off-by: Zubin Mithra <zsm@chromium.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| security/keys/proc.c | 8 ++------ |
| 1 file changed, 2 insertions(+), 6 deletions(-) |
| |
| --- a/security/keys/proc.c |
| +++ b/security/keys/proc.c |
| @@ -187,7 +187,7 @@ static int proc_keys_show(struct seq_fil |
| |
| struct keyring_search_context ctx = { |
| .index_key = key->index_key, |
| - .cred = current_cred(), |
| + .cred = m->file->f_cred, |
| .match_data.cmp = lookup_user_key_possessed, |
| .match_data.raw_data = key, |
| .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, |
| @@ -207,11 +207,7 @@ static int proc_keys_show(struct seq_fil |
| } |
| } |
| |
| - /* check whether the current task is allowed to view the key (assuming |
| - * non-possession) |
| - * - the caller holds a spinlock, and thus the RCU read lock, making our |
| - * access to __current_cred() safe |
| - */ |
| + /* check whether the current task is allowed to view the key */ |
| rc = key_task_permission(key_ref, ctx.cred, KEY_NEED_VIEW); |
| if (rc < 0) |
| return 0; |
