The patch titled
Subject: ipc: introduce lockless pre_down ipcctl
has been added to the -mm tree. Its filename is
ipc-introduce-lockless-pre_down-ipcctl.patch
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------------------------------------------------------
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Subject: 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: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Chegu Vinod <chegu_vinod@xxxxxx>
Cc: Emmanuel Benisty <benisty.e@xxxxxxxxx>
Cc: Jason Low <jason.low2@xxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/util.c | 31 ++++++++++++++++++++++++++-----
ipc/util.h | 3 +++
2 files changed, 29 insertions(+), 5 deletions(-)
diff -puN ipc/util.c~ipc-introduce-lockless-pre_down-ipcctl ipc/util.c
--- a/ipc/util.c~ipc-introduce-lockless-pre_down-ipcctl
+++ a/ipc/util.c
@@ -823,11 +823,28 @@ struct kern_ipc_perm *ipcctl_pre_down(st
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;
@@ -836,17 +853,21 @@ struct kern_ipc_perm *ipcctl_pre_down(st
audit_ipc_obj(ipcp);
if (cmd == IPC_SET)
audit_ipc_set_perm(extra_perm, perm->uid,
- perm->gid, perm->mode);
+ perm->gid, perm->mode);
euid = current_euid();
if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid) ||
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);
}
diff -puN ipc/util.h~ipc-introduce-lockless-pre_down-ipcctl ipc/util.h
--- a/ipc/util.h~ipc-introduce-lockless-pre_down-ipcctl
+++ a/ipc/util.h
@@ -128,6 +128,9 @@ struct kern_ipc_perm *ipc_obtain_object(
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);
_
Patches currently in -mm which might be from davidlohr.bueso@xxxxxx are
lib-int_sqrtc-optimize-square-root-algorithm.patch
ipc-remove-bogus-lock-comment-for-ipc_checkid.patch
ipc-introduce-obtaining-a-lockless-ipc-object.patch
ipc-introduce-obtaining-a-lockless-ipc-object-fix.patch
ipc-introduce-lockless-pre_down-ipcctl.patch
ipcsem-do-not-hold-ipc-lock-more-than-necessary.patch
ipcsem-open-code-and-rename-sem_lock.patch
ipcsem-open-code-and-rename-sem_lock-fix.patch
ipcsem-have-only-one-list-in-struct-sem_queue.patch
ipcsem-fine-grained-locking-for-semtimedop.patch
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