linux-security-module.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Eric Biggers <ebiggers@kernel.org>
To: keyrings@vger.kernel.org, David Howells <dhowells@redhat.com>
Cc: linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH v2] KEYS: always initialize keyring_index_key::desc_len
Date: Thu, 7 Feb 2019 15:35:30 -0800	[thread overview]
Message-ID: <20190207233529.GB125156@gmail.com> (raw)
In-Reply-To: <20190110202744.GA149637@gmail.com>

On Thu, Jan 10, 2019 at 12:27:46PM -0800, Eric Biggers wrote:
> On Wed, Nov 28, 2018 at 03:19:41PM -0800, Eric Biggers wrote:
> > On Fri, Nov 02, 2018 at 06:58:54PM -0700, Eric Biggers wrote:
> > > From: Eric Biggers <ebiggers@google.com>
> > > 
> > > syzbot hit the 'BUG_ON(index_key->desc_len == 0);' in __key_link_begin()
> > > called from construct_alloc_key() during sys_request_key(), because the
> > > length of the key description was never calculated.
> > > 
> > > The problem is that we rely on ->desc_len being initialized by
> > > search_process_keyrings(), specifically by search_nested_keyrings().
> > > But, if the process isn't subscribed to any keyrings that never happens.
> > > 
> > > Fix it by always initializing keyring_index_key::desc_len as soon as the
> > > description is set, like we already do in some places.
> > > 
> > > The following program reproduces the BUG_ON() when it's run as root and
> > > no session keyring has been installed.  If it doesn't work, try removing
> > > pam_keyinit.so from /etc/pam.d/login and rebooting.
> > > 
> > >     #include <stdlib.h>
> > >     #include <unistd.h>
> > >     #include <keyutils.h>
> > > 
> > >     int main(void)
> > >     {
> > >             int id = add_key("keyring", "syz", NULL, 0, KEY_SPEC_USER_KEYRING);
> > > 
> > >             keyctl_setperm(id, KEY_OTH_WRITE);
> > >             setreuid(5000, 5000);
> > >             request_key("user", "desc", "", id);
> > >     }
> > > 
> > > Reported-by: syzbot+ec24e95ea483de0a24da@syzkaller.appspotmail.com
> > > Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
> > > Cc: <stable@vger.kernel.org> # v3.13+
> > > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > > ---
> > > 
> > > v2: In proc_keys_show(), assign index_key directly
> > > 
> > >  security/keys/keyring.c          | 4 +---
> > >  security/keys/proc.c             | 3 +--
> > >  security/keys/request_key.c      | 1 +
> > >  security/keys/request_key_auth.c | 2 +-
> > >  4 files changed, 4 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/security/keys/keyring.c b/security/keys/keyring.c
> > > index 41bcf57e96f21..99a55145ddcd2 100644
> > > --- a/security/keys/keyring.c
> > > +++ b/security/keys/keyring.c
> > > @@ -661,9 +661,6 @@ static bool search_nested_keyrings(struct key *keyring,
> > >  	BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
> > >  	       (ctx->flags & STATE_CHECKS) == STATE_CHECKS);
> > >  
> > > -	if (ctx->index_key.description)
> > > -		ctx->index_key.desc_len = strlen(ctx->index_key.description);
> > > -
> > >  	/* Check to see if this top-level keyring is what we are looking for
> > >  	 * and whether it is valid or not.
> > >  	 */
> > > @@ -914,6 +911,7 @@ key_ref_t keyring_search(key_ref_t keyring,
> > >  	struct keyring_search_context ctx = {
> > >  		.index_key.type		= type,
> > >  		.index_key.description	= description,
> > > +		.index_key.desc_len	= strlen(description),
> > >  		.cred			= current_cred(),
> > >  		.match_data.cmp		= key_default_cmp,
> > >  		.match_data.raw_data	= description,
> > > diff --git a/security/keys/proc.c b/security/keys/proc.c
> > > index 5af2934965d80..d38be9db2cc07 100644
> > > --- a/security/keys/proc.c
> > > +++ b/security/keys/proc.c
> > > @@ -166,8 +166,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
> > >  	int rc;
> > >  
> > >  	struct keyring_search_context ctx = {
> > > -		.index_key.type		= key->type,
> > > -		.index_key.description	= key->description,
> > > +		.index_key		= key->index_key,
> > >  		.cred			= m->file->f_cred,
> > >  		.match_data.cmp		= lookup_user_key_possessed,
> > >  		.match_data.raw_data	= key,
> > > diff --git a/security/keys/request_key.c b/security/keys/request_key.c
> > > index 114f7408feee6..7385536986497 100644
> > > --- a/security/keys/request_key.c
> > > +++ b/security/keys/request_key.c
> > > @@ -545,6 +545,7 @@ struct key *request_key_and_link(struct key_type *type,
> > >  	struct keyring_search_context ctx = {
> > >  		.index_key.type		= type,
> > >  		.index_key.description	= description,
> > > +		.index_key.desc_len	= strlen(description),
> > >  		.cred			= current_cred(),
> > >  		.match_data.cmp		= key_default_cmp,
> > >  		.match_data.raw_data	= description,
> > > diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
> > > index 424e1d90412ea..6797843154f03 100644
> > > --- a/security/keys/request_key_auth.c
> > > +++ b/security/keys/request_key_auth.c
> > > @@ -246,7 +246,7 @@ struct key *key_get_instantiation_authkey(key_serial_t target_id)
> > >  	struct key *authkey;
> > >  	key_ref_t authkey_ref;
> > >  
> > > -	sprintf(description, "%x", target_id);
> > > +	ctx.index_key.desc_len = sprintf(description, "%x", target_id);
> > >  
> > >  	authkey_ref = search_process_keyrings(&ctx);
> > >  
> > > -- 
> > > 2.19.1
> > > 
> > 
> > Ping.  David, are you planning to apply this?
> > 
> > - Eric
> > 
> > -- 
> > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20181128231940.GB131170%40gmail.com.
> > For more options, visit https://groups.google.com/d/optout.
> 
> Ping.
> 

Ping.  David, are you planning to apply this?

- Eric

  reply	other threads:[~2019-02-07 23:35 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-05 11:16 kernel BUG at security/keys/keyring.c:LINE! syzbot
2018-11-02 23:15 ` [PATCH] KEYS: always initialize keyring_index_key::desc_len Eric Biggers
2018-11-03  1:57   ` Eric Biggers
2018-11-03  1:58 ` [PATCH v2] " Eric Biggers
2018-11-28 23:19   ` Eric Biggers
2018-12-06 18:26     ` Eric Biggers
2019-01-10 20:27     ` Eric Biggers
2019-02-07 23:35       ` Eric Biggers [this message]
2019-02-19 23:04         ` Eric Biggers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190207233529.GB125156@gmail.com \
    --to=ebiggers@kernel.org \
    --cc=dhowells@redhat.com \
    --cc=keyrings@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=syzkaller-bugs@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).