Revision 712f3147aee0fbbbbed2da20b21b272c5505125e authored by Linus Torvalds on 13 May 2011, 23:16:41 UTC, committed by Linus Torvalds on 14 May 2011, 17:23:44 UTC
When a register_framebuffer() call results in us removing old conflicting framebuffers, the new registration_lock doesn't protect that situation. And we can't just add the same locking to the function, because these functions call each other: register_framebuffer() calls remove_conflicting_framebuffers, which in turn calls unregister_framebuffer for any conflicting entry. In order to fix it, this just creates wrapper functions around all three functions and makes the versions that actually do the work be called "do_xxx()", leaving just the wrapper that gets the lock and calls the worker function. So the rule becomes simply that "do_xxxx()" has to be called with the lock held, and now do_register_framebuffer() can just call do_remove_conflicting_framebuffers(), and that in turn can call _do_unregister_framebuffer(), and there is no deadlock, and we can hold the registration lock over the whole sequence, fixing the races. It also makes error cases simpler, and fixes one situation where we would return from unregister_framebuffer() without releasing the lock, pointed out by Bruno Prémont. Tested-by: Bruno Prémont <bonbons@linux-vserver.org> Tested-by: Anca Emanuel <anca.emanuel@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent c47747f
auth_generic.c
/*
* Generic RPC credential
*
* Copyright (C) 2008, Trond Myklebust <Trond.Myklebust@netapp.com>
*/
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/sunrpc/auth.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/debug.h>
#include <linux/sunrpc/sched.h>
#ifdef RPC_DEBUG
# define RPCDBG_FACILITY RPCDBG_AUTH
#endif
#define RPC_MACHINE_CRED_USERID ((uid_t)0)
#define RPC_MACHINE_CRED_GROUPID ((gid_t)0)
struct generic_cred {
struct rpc_cred gc_base;
struct auth_cred acred;
};
static struct rpc_auth generic_auth;
static const struct rpc_credops generic_credops;
/*
* Public call interface
*/
struct rpc_cred *rpc_lookup_cred(void)
{
return rpcauth_lookupcred(&generic_auth, 0);
}
EXPORT_SYMBOL_GPL(rpc_lookup_cred);
/*
* Public call interface for looking up machine creds.
*/
struct rpc_cred *rpc_lookup_machine_cred(void)
{
struct auth_cred acred = {
.uid = RPC_MACHINE_CRED_USERID,
.gid = RPC_MACHINE_CRED_GROUPID,
.machine_cred = 1,
};
dprintk("RPC: looking up machine cred\n");
return generic_auth.au_ops->lookup_cred(&generic_auth, &acred, 0);
}
EXPORT_SYMBOL_GPL(rpc_lookup_machine_cred);
static struct rpc_cred *generic_bind_cred(struct rpc_task *task,
struct rpc_cred *cred, int lookupflags)
{
struct rpc_auth *auth = task->tk_client->cl_auth;
struct auth_cred *acred = &container_of(cred, struct generic_cred, gc_base)->acred;
return auth->au_ops->lookup_cred(auth, acred, lookupflags);
}
/*
* Lookup generic creds for current process
*/
static struct rpc_cred *
generic_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
return rpcauth_lookup_credcache(&generic_auth, acred, flags);
}
static struct rpc_cred *
generic_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
struct generic_cred *gcred;
gcred = kmalloc(sizeof(*gcred), GFP_KERNEL);
if (gcred == NULL)
return ERR_PTR(-ENOMEM);
rpcauth_init_cred(&gcred->gc_base, acred, &generic_auth, &generic_credops);
gcred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_UPTODATE;
gcred->acred.uid = acred->uid;
gcred->acred.gid = acred->gid;
gcred->acred.group_info = acred->group_info;
if (gcred->acred.group_info != NULL)
get_group_info(gcred->acred.group_info);
gcred->acred.machine_cred = acred->machine_cred;
dprintk("RPC: allocated %s cred %p for uid %d gid %d\n",
gcred->acred.machine_cred ? "machine" : "generic",
gcred, acred->uid, acred->gid);
return &gcred->gc_base;
}
static void
generic_free_cred(struct rpc_cred *cred)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
dprintk("RPC: generic_free_cred %p\n", gcred);
if (gcred->acred.group_info != NULL)
put_group_info(gcred->acred.group_info);
kfree(gcred);
}
static void
generic_free_cred_callback(struct rcu_head *head)
{
struct rpc_cred *cred = container_of(head, struct rpc_cred, cr_rcu);
generic_free_cred(cred);
}
static void
generic_destroy_cred(struct rpc_cred *cred)
{
call_rcu(&cred->cr_rcu, generic_free_cred_callback);
}
/*
* Match credentials against current process creds.
*/
static int
generic_match(struct auth_cred *acred, struct rpc_cred *cred, int flags)
{
struct generic_cred *gcred = container_of(cred, struct generic_cred, gc_base);
int i;
if (gcred->acred.uid != acred->uid ||
gcred->acred.gid != acred->gid ||
gcred->acred.machine_cred != acred->machine_cred)
goto out_nomatch;
/* Optimisation in the case where pointers are identical... */
if (gcred->acred.group_info == acred->group_info)
goto out_match;
/* Slow path... */
if (gcred->acred.group_info->ngroups != acred->group_info->ngroups)
goto out_nomatch;
for (i = 0; i < gcred->acred.group_info->ngroups; i++) {
if (GROUP_AT(gcred->acred.group_info, i) !=
GROUP_AT(acred->group_info, i))
goto out_nomatch;
}
out_match:
return 1;
out_nomatch:
return 0;
}
int __init rpc_init_generic_auth(void)
{
return rpcauth_init_credcache(&generic_auth);
}
void rpc_destroy_generic_auth(void)
{
rpcauth_destroy_credcache(&generic_auth);
}
static const struct rpc_authops generic_auth_ops = {
.owner = THIS_MODULE,
.au_name = "Generic",
.lookup_cred = generic_lookup_cred,
.crcreate = generic_create_cred,
};
static struct rpc_auth generic_auth = {
.au_ops = &generic_auth_ops,
.au_count = ATOMIC_INIT(0),
};
static const struct rpc_credops generic_credops = {
.cr_name = "Generic cred",
.crdestroy = generic_destroy_cred,
.crbind = generic_bind_cred,
.crmatch = generic_match,
};
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