Through ipc_lock() and, therefore, ipc_lock_check() we currently
return the locked ipc object. This is not necessary for all situations,
thus introduce, analogous, ipc_obtain_object and ipc_obtain_object_check
functions that only mark the RCU read critical region without acquiring
the lock and return the ipc object.
Signed-off-by: Davidlohr Bueso <davidlohr.bu...@hp.com>
---
ipc/util.c | 42 ++++++++++++++++++++++++++++++++----------
ipc/util.h | 2 ++
2 files changed, 34 insertions(+), 10 deletions(-)
diff --git a/ipc/util.c b/ipc/util.c
index 464a8ab..902f282 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -667,6 +667,21 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct
ipc_perm *out)
out->seq = in->seq;
}
+struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
+{
+ struct kern_ipc_perm *out;
+ int lid = ipcid_to_idx(id);
+
+ rcu_read_lock();
+ out = idr_find(&ids->ipcs_idr, lid);
+ if (!out) {
+ rcu_read_unlock();
+ return ERR_PTR(-EINVAL);
+ }
+
+ return out;
+}
+
/**
* ipc_lock - Lock an ipc structure without rw_mutex held
* @ids: IPC identifier set
@@ -679,18 +694,13 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in,
struct ipc_perm *out)
struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
{
- struct kern_ipc_perm *out;
- int lid = ipcid_to_idx(id);
+ struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
- rcu_read_lock();
- out = idr_find(&ids->ipcs_idr, lid);
- if (out == NULL) {
- rcu_read_unlock();
+ if (!out)
return ERR_PTR(-EINVAL);
- }
spin_lock(&out->lock);
-
+
/* ipc_rmid() may have already freed the ID while ipc_lock
* was spinning: here verify that the structure is still valid
*/
@@ -703,6 +713,18 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
return out;
}
+struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
+{
+ struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
+
+ if (IS_ERR(out))
+ return out;
+
+ if (ipc_checkid(out, id))
+ return ERR_PTR(-EIDRM);
+ return out;
+}
+
struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
{
struct kern_ipc_perm *out;
@@ -784,7 +806,7 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace
*ns,
int err;
down_write(&ids->rw_mutex);
- ipcp = ipc_lock_check(ids, id);
+ ipcp = ipc_obtain_object_check(ids, id);
if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp);
goto out_up;
@@ -801,7 +823,7 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace
*ns,
return ipcp;
err = -EPERM;
- ipc_unlock(ipcp);
+ rcu_read_unlock();
out_up:
up_write(&ids->rw_mutex);
return ERR_PTR(err);
diff --git a/ipc/util.h b/ipc/util.h
index eeb79a1..2c68035 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -123,6 +123,7 @@ void ipc_rcu_getref(void *ptr);
void ipc_rcu_putref(void *ptr);
struct kern_ipc_perm *ipc_lock(struct ipc_ids *, int);
+struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id);
void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out);
void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out);
@@ -173,6 +174,7 @@ static inline void ipc_unlock(struct kern_ipc_perm *perm)
}
struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id);
+struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id);
int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
struct ipc_ops *ops, struct ipc_params *params);
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
--
1.7.11.7
--
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