On 12/6/2024 12:05 PM, Kees Bakker wrote:
> Op 23-10-2024 om 23:21 schreef Casey Schaufler:
>> Add a new lsm_context data structure to hold all the information about a
>> "security context", including the string, its size and which LSM
>> allocated
>> the string. The allocation information is necessary because LSMs have
>> different policies regarding the lifecycle of these strings. SELinux
>> allocates and destroys them on each use, whereas Smack provides a
>> pointer
>> to an entry in a list that never goes away.
>>
>> Update security_release_secctx() to use the lsm_context instead of a
>> (char *, len) pair. Change its callers to do likewise. The LSMs
>> supporting this hook have had comments added to remind the developer
>> that there is more work to be done.
>>
>> The BPF security module provides all LSM hooks. While there has yet to
>> be a known instance of a BPF configuration that uses security contexts,
>> the possibility is real. In the existing implementation there is
>> potential for multiple frees in that case.
>>
>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> Cc: linux-integrity@xxxxxxxxxxxxxxx
>> Cc: netdev@xxxxxxxxxxxxxxx
>> Cc: audit@xxxxxxxxxxxxxxx
>> Cc: netfilter-devel@xxxxxxxxxxxxxxx
>> To: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
>> Cc: linux-nfs@xxxxxxxxxxxxxxx
>> Cc: Todd Kjos <tkjos@xxxxxxxxxx>
>> ---
>> drivers/android/binder.c | 24 +++++++--------
>> fs/ceph/xattr.c | 6 +++-
>> fs/nfs/nfs4proc.c | 8 +++--
>> fs/nfsd/nfs4xdr.c | 8 +++--
>> include/linux/lsm_hook_defs.h | 2 +-
>> include/linux/security.h | 35 ++++++++++++++++++++--
>> include/net/scm.h | 11 +++----
>> kernel/audit.c | 30 +++++++++----------
>> kernel/auditsc.c | 23 +++++++-------
>> net/ipv4/ip_sockglue.c | 10 +++----
>> net/netfilter/nf_conntrack_netlink.c | 10 +++----
>> net/netfilter/nf_conntrack_standalone.c | 9 +++---
>> net/netfilter/nfnetlink_queue.c | 13 +++++---
>> net/netlabel/netlabel_unlabeled.c | 40 +++++++++++--------------
>> net/netlabel/netlabel_user.c | 11 ++++---
>> security/apparmor/include/secid.h | 2 +-
>> security/apparmor/secid.c | 11 +++++--
>> security/security.c | 8 ++---
>> security/selinux/hooks.c | 11 +++++--
>> 19 files changed, 165 insertions(+), 107 deletions(-)
>>
>> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
>> index 978740537a1a..d4229bf6f789 100644
>> --- a/drivers/android/binder.c
>> +++ b/drivers/android/binder.c
>> @@ -3011,8 +3011,7 @@ static void binder_transaction(struct
>> binder_proc *proc,
>> struct binder_context *context = proc->context;
>> int t_debug_id = atomic_inc_return(&binder_last_id);
>> ktime_t t_start_time = ktime_get();
>> - char *secctx = NULL;
>> - u32 secctx_sz = 0;
>> + struct lsm_context lsmctx;
> Not initialized ?
Thank you for the review.
It makes sense to initialize it here. I will make the change.
>> struct list_head sgc_head;
>> struct list_head pf_head;
>> const void __user *user_buffer = (const void __user *)
>> @@ -3291,7 +3290,8 @@ static void binder_transaction(struct
>> binder_proc *proc,
>> size_t added_size;
>> security_cred_getsecid(proc->cred, &secid);
>> - ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
>> + ret = security_secid_to_secctx(secid, &lsmctx.context,
>> + &lsmctx.len);
>> if (ret) {
>> binder_txn_error("%d:%d failed to get security context\n",
>> thread->pid, proc->pid);
>> @@ -3300,7 +3300,7 @@ static void binder_transaction(struct
>> binder_proc *proc,
>> return_error_line = __LINE__;
>> goto err_get_secctx_failed;
>> }
>> - added_size = ALIGN(secctx_sz, sizeof(u64));
>> + added_size = ALIGN(lsmctx.len, sizeof(u64));
>> extra_buffers_size += added_size;
>> if (extra_buffers_size < added_size) {
>> binder_txn_error("%d:%d integer overflow of
>> extra_buffers_size\n",
>> @@ -3334,23 +3334,23 @@ static void binder_transaction(struct
>> binder_proc *proc,
>> t->buffer = NULL;
>> goto err_binder_alloc_buf_failed;
>> }
>> - if (secctx) {
>> + if (lsmctx.context) {
> From code inspection it is not immediately obvious. Can you
> guarantee that lsmctx is always initialized when the code
> gets to this point? Perhaps it is safer to just initialize when
> it is defined above (line 3014).
>
>
