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ipc/sem: use flexible array in 'struct sem_undo'

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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>
This commit is contained in:
Christophe JAILLET 2023-07-09 18:12:55 +02:00 committed by Andrew Morton
parent 4264be505d
commit b46fae0615
1 changed files with 2 additions and 4 deletions
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6
ipc/sem.c
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@ -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);