Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 444d0f62 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
Browse files

ipc: introduce lockless pre_down ipcctl 



Various forms of ipc use ipcctl_pre_down() to retrieve an ipc object and
check permissions, mostly for IPC_RMID and IPC_SET commands.

Introduce ipcctl_pre_down_nolock(), a lockless version of this function.
The locking version is retained, yet modified to call the nolock version
without affecting its semantics, thus transparent to all ipc callers.

Signed-off-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4d2bff5e

ipc/util.c

+26 −5
Original line number Diff line number Diff line
@@ -824,11 +824,28 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns, 
				      struct ipc64_perm *perm, int extra_perm)

{

	struct kern_ipc_perm *ipcp;



	ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm);

	if (IS_ERR(ipcp))

		goto out;



	spin_lock(&ipcp->lock);

out:

	return ipcp;

}



struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,

					     struct ipc_ids *ids, int id, int cmd,

					     struct ipc64_perm *perm, int extra_perm)

{

	kuid_t euid;

	int err;

	int err = -EPERM;

	struct kern_ipc_perm *ipcp;



	down_write(&ids->rw_mutex);

	ipcp = ipc_lock_check(ids, id);

	rcu_read_lock();



	ipcp = ipc_obtain_object_check(ids, id);

	if (IS_ERR(ipcp)) {

		err = PTR_ERR(ipcp);

		goto out_up;
@@ -844,10 +861,14 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns, 
	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))

		return ipcp;



	err = -EPERM;

	ipc_unlock(ipcp);

out_up:

	/*

	 * Unsuccessful lookup, unlock and return

	 * the corresponding error.

	 */

	rcu_read_unlock();

	up_write(&ids->rw_mutex);



	return ERR_PTR(err);

}

ipc/util.h

+3 −0
Original line number Diff line number Diff line
@@ -128,6 +128,9 @@ 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);

int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out);

struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,

					     struct ipc_ids *ids, int id, int cmd,

					     struct ipc64_perm *perm, int extra_perm);

struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,

				      struct ipc_ids *ids, int id, int cmd,

				      struct ipc64_perm *perm, int extra_perm);