![Scott Mayhew](/assets/img/avatar_default.png)
A generic_cred can be used to look up a unx_cred or a gss_cred, so it's not really safe to use the the generic_cred->acred->ac_flags to store the NO_CRKEY_TIMEOUT flag. A lookup for a unx_cred triggered while the KEY_EXPIRE_SOON flag is already set will cause both NO_CRKEY_TIMEOUT and KEY_EXPIRE_SOON to be set in the ac_flags, leaving the user associated with the auth_cred to be in a state where they're perpetually doing 4K NFS_FILE_SYNC writes. This can be reproduced as follows: 1. Mount two NFS filesystems, one with sec=krb5 and one with sec=sys. They do not need to be the same export, nor do they even need to be from the same NFS server. Also, v3 is fine. $ sudo mount -o v3,sec=krb5 server1:/export /mnt/krb5 $ sudo mount -o v3,sec=sys server2:/export /mnt/sys 2. As the normal user, before accessing the kerberized mount, kinit with a short lifetime (but not so short that renewing the ticket would leave you within the 4-minute window again by the time the original ticket expires), e.g. $ kinit -l 10m -r 60m 3. Do some I/O to the kerberized mount and verify that the writes are wsize, UNSTABLE: $ dd if=/dev/zero of=/mnt/krb5/file bs=1M count=1 4. Wait until you're within 4 minutes of key expiry, then do some more I/O to the kerberized mount to ensure that RPC_CRED_KEY_EXPIRE_SOON gets set. Verify that the writes are 4K, FILE_SYNC: $ dd if=/dev/zero of=/mnt/krb5/file bs=1M count=1 5. Now do some I/O to the sec=sys mount. This will cause RPC_CRED_NO_CRKEY_TIMEOUT to be set: $ dd if=/dev/zero of=/mnt/sys/file bs=1M count=1 6. Writes for that user will now be permanently 4K, FILE_SYNC for that user, regardless of which mount is being written to, until you reboot the client. Renewing the kerberos ticket (assuming it hasn't already expired) will have no effect. Grabbing a new kerberos ticket at this point will have no effect either. Move the flag to the auth->au_flags field (which is currently unused) and rename it slightly to reflect that it's no longer associated with the auth_cred->ac_flags. Add the rpc_auth to the arg list of rpcauth_cred_key_to_expire and check the au_flags there too. Finally, add the inode to the arg list of nfs_ctx_key_to_expire so we can determine the rpc_auth to pass to rpcauth_cred_key_to_expire. Signed-off-by: Scott Mayhew <smayhew@redhat.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
291 lines
7.7 KiB
C
291 lines
7.7 KiB
C
/*
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* Generic RPC credential
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*
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* Copyright (C) 2008, Trond Myklebust <Trond.Myklebust@netapp.com>
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*/
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/sunrpc/auth.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/sunrpc/debug.h>
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#include <linux/sunrpc/sched.h>
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#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
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# define RPCDBG_FACILITY RPCDBG_AUTH
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#endif
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#define RPC_MACHINE_CRED_USERID GLOBAL_ROOT_UID
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#define RPC_MACHINE_CRED_GROUPID GLOBAL_ROOT_GID
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struct generic_cred {
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struct rpc_cred gc_base;
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struct auth_cred acred;
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};
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static struct rpc_auth generic_auth;
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static const struct rpc_credops generic_credops;
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/*
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* Public call interface
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*/
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struct rpc_cred *rpc_lookup_cred(void)
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{
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return rpcauth_lookupcred(&generic_auth, 0);
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}
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EXPORT_SYMBOL_GPL(rpc_lookup_cred);
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struct rpc_cred *
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rpc_lookup_generic_cred(struct auth_cred *acred, int flags, gfp_t gfp)
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{
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return rpcauth_lookup_credcache(&generic_auth, acred, flags, gfp);
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}
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EXPORT_SYMBOL_GPL(rpc_lookup_generic_cred);
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struct rpc_cred *rpc_lookup_cred_nonblock(void)
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{
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return rpcauth_lookupcred(&generic_auth, RPCAUTH_LOOKUP_RCU);
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}
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EXPORT_SYMBOL_GPL(rpc_lookup_cred_nonblock);
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/*
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* Public call interface for looking up machine creds.
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*/
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struct rpc_cred *rpc_lookup_machine_cred(const char *service_name)
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{
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struct auth_cred acred = {
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.uid = RPC_MACHINE_CRED_USERID,
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.gid = RPC_MACHINE_CRED_GROUPID,
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.principal = service_name,
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.machine_cred = 1,
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};
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dprintk("RPC: looking up machine cred for service %s\n",
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service_name);
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return generic_auth.au_ops->lookup_cred(&generic_auth, &acred, 0);
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}
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EXPORT_SYMBOL_GPL(rpc_lookup_machine_cred);
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static struct rpc_cred *generic_bind_cred(struct rpc_task *task,
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struct rpc_cred *cred, int lookupflags)
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{
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struct rpc_auth *auth = task->tk_client->cl_auth;
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struct auth_cred *acred = &container_of(cred, struct generic_cred, gc_base)->acred;
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return auth->au_ops->lookup_cred(auth, acred, lookupflags);
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}
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/*
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* Lookup generic creds for current process
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*/
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static struct rpc_cred *
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generic_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
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{
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return rpcauth_lookup_credcache(&generic_auth, acred, flags, GFP_KERNEL);
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}
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static struct rpc_cred *
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generic_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags, gfp_t gfp)
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{
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struct generic_cred *gcred;
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gcred = kmalloc(sizeof(*gcred), gfp);
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if (gcred == NULL)
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return ERR_PTR(-ENOMEM);
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rpcauth_init_cred(&gcred->gc_base, acred, &generic_auth, &generic_credops);
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gcred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;
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gcred->acred.uid = acred->uid;
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gcred->acred.gid = acred->gid;
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gcred->acred.group_info = acred->group_info;
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gcred->acred.ac_flags = 0;
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if (gcred->acred.group_info != NULL)
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get_group_info(gcred->acred.group_info);
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gcred->acred.machine_cred = acred->machine_cred;
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gcred->acred.principal = acred->principal;
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dprintk("RPC: allocated %s cred %p for uid %d gid %d\n",
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gcred->acred.machine_cred ? "machine" : "generic",
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gcred,
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from_kuid(&init_user_ns, acred->uid),
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from_kgid(&init_user_ns, acred->gid));
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return &gcred->gc_base;
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}
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static void
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generic_free_cred(struct rpc_cred *cred)
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{
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struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
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dprintk("RPC: generic_free_cred %p\n", gcred);
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if (gcred->acred.group_info != NULL)
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put_group_info(gcred->acred.group_info);
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kfree(gcred);
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}
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static void
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generic_free_cred_callback(struct rcu_head *head)
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{
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struct rpc_cred *cred = container_of(head, struct rpc_cred, cr_rcu);
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generic_free_cred(cred);
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}
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static void
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generic_destroy_cred(struct rpc_cred *cred)
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{
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call_rcu(&cred->cr_rcu, generic_free_cred_callback);
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}
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static int
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machine_cred_match(struct auth_cred *acred, struct generic_cred *gcred, int flags)
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{
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if (!gcred->acred.machine_cred ||
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gcred->acred.principal != acred->principal ||
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!uid_eq(gcred->acred.uid, acred->uid) ||
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!gid_eq(gcred->acred.gid, acred->gid))
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return 0;
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return 1;
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}
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/*
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* Match credentials against current process creds.
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*/
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static int
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generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
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{
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struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
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int i;
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if (acred->machine_cred)
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return machine_cred_match(acred, gcred, flags);
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if (!uid_eq(gcred->acred.uid, acred->uid) ||
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!gid_eq(gcred->acred.gid, acred->gid) ||
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gcred->acred.machine_cred != 0)
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goto out_nomatch;
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/* Optimisation in the case where pointers are identical... */
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if (gcred->acred.group_info == acred->group_info)
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goto out_match;
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/* Slow path... */
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if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
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goto out_nomatch;
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for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
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if (!gid_eq(GROUP_AT(gcred->acred.group_info, i),
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GROUP_AT(acred->group_info, i)))
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goto out_nomatch;
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}
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out_match:
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return 1;
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out_nomatch:
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return 0;
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}
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int __init rpc_init_generic_auth(void)
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{
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return rpcauth_init_credcache(&generic_auth);
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}
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void rpc_destroy_generic_auth(void)
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{
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rpcauth_destroy_credcache(&generic_auth);
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}
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/*
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* Test the the current time (now) against the underlying credential key expiry
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* minus a timeout and setup notification.
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*
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* The normal case:
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* If 'now' is before the key expiry minus RPC_KEY_EXPIRE_TIMEO, set
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* the RPC_CRED_NOTIFY_TIMEOUT flag to setup the underlying credential
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* rpc_credops crmatch routine to notify this generic cred when it's key
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* expiration is within RPC_KEY_EXPIRE_TIMEO, and return 0.
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*
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* The error case:
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* If the underlying cred lookup fails, return -EACCES.
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*
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* The 'almost' error case:
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* If 'now' is within key expiry minus RPC_KEY_EXPIRE_TIMEO, but not within
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* key expiry minus RPC_KEY_EXPIRE_FAIL, set the RPC_CRED_EXPIRE_SOON bit
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* on the acred ac_flags and return 0.
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*/
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static int
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generic_key_timeout(struct rpc_auth *auth, struct rpc_cred *cred)
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{
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struct auth_cred *acred = &container_of(cred, struct generic_cred,
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gc_base)->acred;
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struct rpc_cred *tcred;
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int ret = 0;
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/* Fast track for non crkey_timeout (no key) underlying credentials */
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if (auth->au_flags & RPCAUTH_AUTH_NO_CRKEY_TIMEOUT)
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return 0;
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/* Fast track for the normal case */
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if (test_bit(RPC_CRED_NOTIFY_TIMEOUT, &acred->ac_flags))
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return 0;
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/* lookup_cred either returns a valid referenced rpc_cred, or PTR_ERR */
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tcred = auth->au_ops->lookup_cred(auth, acred, 0);
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if (IS_ERR(tcred))
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return -EACCES;
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/* Test for the almost error case */
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ret = tcred->cr_ops->crkey_timeout(tcred);
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if (ret != 0) {
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set_bit(RPC_CRED_KEY_EXPIRE_SOON, &acred->ac_flags);
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ret = 0;
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} else {
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/* In case underlying cred key has been reset */
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if (test_and_clear_bit(RPC_CRED_KEY_EXPIRE_SOON,
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&acred->ac_flags))
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dprintk("RPC: UID %d Credential key reset\n",
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from_kuid(&init_user_ns, tcred->cr_uid));
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/* set up fasttrack for the normal case */
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set_bit(RPC_CRED_NOTIFY_TIMEOUT, &acred->ac_flags);
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}
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put_rpccred(tcred);
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return ret;
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}
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static const struct rpc_authops generic_auth_ops = {
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.owner = THIS_MODULE,
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.au_name = "Generic",
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.lookup_cred = generic_lookup_cred,
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.crcreate = generic_create_cred,
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.key_timeout = generic_key_timeout,
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};
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static struct rpc_auth generic_auth = {
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.au_ops = &generic_auth_ops,
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.au_count = ATOMIC_INIT(0),
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};
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static bool generic_key_to_expire(struct rpc_cred *cred)
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{
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struct auth_cred *acred = &container_of(cred, struct generic_cred,
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gc_base)->acred;
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bool ret;
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get_rpccred(cred);
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ret = test_bit(RPC_CRED_KEY_EXPIRE_SOON, &acred->ac_flags);
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put_rpccred(cred);
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return ret;
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}
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static const struct rpc_credops generic_credops = {
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.cr_name = "Generic cred",
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.crdestroy = generic_destroy_cred,
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.crbind = generic_bind_cred,
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.crmatch = generic_match,
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.crkey_to_expire = generic_key_to_expire,
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};
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