The patch titled
Subject: ipc/sem: avoid ipc_rcu_alloc()
has been added to the -mm tree. Its filename is
ipc-sem-avoid-ipc_rcu_alloc.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-sem-avoid-ipc_rcu_alloc.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-sem-avoid-ipc_rcu_alloc.patch
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------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: ipc/sem: avoid ipc_rcu_alloc()
Instead of using ipc_rcu_alloc() which only performs the refcount bump,
open code it to perform better sem-specific checks. This also allows for
sem_array structure layout to be randomized in the future.
[manfred@xxxxxxxxxxxxxxxx: Rediff, because the memset was temporarily inside ipc_rcu_alloc()]
Link: http://lkml.kernel.org/r/20170525185107.12869-10-manfred@xxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff -puN ipc/sem.c~ipc-sem-avoid-ipc_rcu_alloc ipc/sem.c
--- a/ipc/sem.c~ipc-sem-avoid-ipc_rcu_alloc
+++ a/ipc/sem.c
@@ -451,6 +451,25 @@ static inline void sem_rmid(struct ipc_n
ipc_rmid(&sem_ids(ns), &s->sem_perm);
}
+static struct sem_array *sem_alloc(size_t nsems)
+{
+ struct sem_array *sma;
+ size_t size;
+
+ if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
+ return NULL;
+
+ size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
+ sma = kvmalloc(size, GFP_KERNEL);
+ if (unlikely(!sma))
+ return NULL;
+
+ memset(sma, 0, size);
+ atomic_set(&sma->sem_perm.refcount, 1);
+
+ return sma;
+}
+
/**
* newary - Create a new semaphore set
* @ns: namespace
@@ -463,7 +482,6 @@ static int newary(struct ipc_namespace *
int id;
int retval;
struct sem_array *sma;
- int size;
key_t key = params->key;
int nsems = params->u.nsems;
int semflg = params->flg;
@@ -474,10 +492,7 @@ static int newary(struct ipc_namespace *
if (ns->used_sems + nsems > ns->sc_semmns)
return -ENOSPC;
- BUILD_BUG_ON(offsetof(struct sem_array, sem_perm) != 0);
-
- size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
- sma = container_of(ipc_rcu_alloc(size), struct sem_array, sem_perm);
+ sma = sem_alloc(nsems);
if (!sma)
return -ENOMEM;
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
ipc-drop-non-rcu-allocation.patch
ipc-sem-do-not-use-ipc_rcu_free.patch
ipc-shm-do-not-use-ipc_rcu_free.patch
ipc-msg-do-not-use-ipc_rcu_free.patch
ipc-util-drop-ipc_rcu_free.patch
ipc-sem-avoid-ipc_rcu_alloc.patch
ipc-shm-avoid-ipc_rcu_alloc.patch
ipc-msg-avoid-ipc_rcu_alloc.patch
ipc-util-drop-ipc_rcu_alloc.patch
ipc-move-atomic_set-to-where-it-is-needed.patch
ipc-shm-remove-special-shm_alloc-free.patch
ipc-msg-remove-special-msg_alloc-free.patch
ipc-sem-drop-__sem_free.patch
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