From b46fae06153da31a80ab0f3e98819416fc134725 Mon Sep 17 00:00:00 2001
From: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Date: Sun, 9 Jul 2023 18:12:55 +0200
Subject: [PATCH] ipc/sem: use flexible array in 'struct sem_undo'
Turn 'semadj' in 'struct sem_undo' into a flexible array.
The advantages are:
- save the size of a pointer when the new undo structure is allocated
- avoid some always ugly pointer arithmetic to get the address of semadj
- avoid an indirection when the array is accessed
While at it, use struct_size() to compute the size of the new undo
structure.
Link: https://lkml.kernel.org/r/1ba993d443ad7e16ac2b1902adab1f05ebdfa454.1688918791.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Manfred Spraul <manfred@colorfullife.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
ipc/sem.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index 00f88aa01ac5a..a39cdc7bf88fa 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -152,7 +152,7 @@ struct sem_undo {
struct list_head list_id; /* per semaphore array list:
* all undos for one array */
int semid; /* semaphore set identifier */
- short *semadj; /* array of adjustments */
+ short semadj[]; /* array of adjustments */
/* one per semaphore */
};
@@ -1938,8 +1938,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
rcu_read_unlock();
/* step 2: allocate new undo structure */
- new = kvzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems,
- GFP_KERNEL_ACCOUNT);
+ new = kvzalloc(struct_size(new, semadj, nsems), GFP_KERNEL_ACCOUNT);
if (!new) {
ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
return ERR_PTR(-ENOMEM);
@@ -1967,7 +1966,6 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
goto success;
}
/* step 5: initialize & link new undo structure */
- new->semadj = (short *) &new[1];
new->ulp = ulp;
new->semid = semid;
assert_spin_locked(&ulp->lock);
--
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