On Fri, Nov 02, 2018 at 06:58:54PM -0700, Eric Biggers wrote: > From: Eric Biggers <[email protected]> > > 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: [email protected] > Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") > Cc: <[email protected]> # v3.13+ > Signed-off-by: Eric Biggers <[email protected]> > --- > > 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
