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ipc: introduce lockless pre_down ipcctl

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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: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Suggested-by: Linus 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: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso
2013-04-30 19:15:24 -07:00
committed by Linus Torvalds
parent 4d2bff5eb8
commit 444d0f621b
2 changed files with 29 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
ipc/util.c
View File

@@ -824,11 +824,28 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
struct ipc64_perm *perm, int extra_perm) struct ipc64_perm *perm, int extra_perm)
{ {
struct kern_ipc_perm *ipcp; 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; kuid_t euid;
int err; int err = -EPERM;
struct kern_ipc_perm *ipcp;
down_write(&ids->rw_mutex); 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)) { if (IS_ERR(ipcp)) {
err = PTR_ERR(ipcp); err = PTR_ERR(ipcp);
goto out_up; goto out_up;
@@ -837,17 +854,21 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
audit_ipc_obj(ipcp); audit_ipc_obj(ipcp);
if (cmd == IPC_SET) if (cmd == IPC_SET)
audit_ipc_set_perm(extra_perm, perm->uid, audit_ipc_set_perm(extra_perm, perm->uid,
perm->gid, perm->mode); perm->gid, perm->mode);
euid = current_euid(); euid = current_euid();
if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid) || if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid) ||
ns_capable(ns->user_ns, CAP_SYS_ADMIN)) ns_capable(ns->user_ns, CAP_SYS_ADMIN))
return ipcp; return ipcp;
err = -EPERM;
ipc_unlock(ipcp);
out_up: out_up:
/*
* Unsuccessful lookup, unlock and return
* the corresponding error.
*/
rcu_read_unlock();
up_write(&ids->rw_mutex); up_write(&ids->rw_mutex);
return ERR_PTR(err); return ERR_PTR(err);
} }

3
ipc/util.h
View File

@@ -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 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); 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); 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 kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
struct ipc_ids *ids, int id, int cmd, struct ipc_ids *ids, int id, int cmd,
struct ipc64_perm *perm, int extra_perm); struct ipc64_perm *perm, int extra_perm);