From: Eric Biggers <ebigg...@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+ec24e95ea483de0a2...@syzkaller.appspotmail.com
Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
Cc: <sta...@vger.kernel.org> # v3.13+
Signed-off-by: Eric Biggers <ebigg...@google.com>
---
security/keys/keyring.c | 4 +---
security/keys/proc.c | 1 +
security/keys/request_key.c | 1 +
security/keys/request_key_auth.c | 2 +-
4 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 41bcf57e96f2..99a55145ddcd 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 5af2934965d8..909f6c5270a1 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -168,6 +168,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
struct keyring_search_context ctx = {
.index_key.type = key->type,
.index_key.description = key->description,
+ .index_key.desc_len = strlen(key->description),
.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 114f7408feee..738553698649 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 424e1d90412e..6797843154f0 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);
--
2.19.1.930.g4563a0d9d0-goog
