From b46fae06153da31a80ab0f3e98819416fc134725 Mon Sep 17 00:00:00 2001 From: Christophe JAILLET 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 Reviewed-by: Manfred Spraul Reviewed-by: Davidlohr Bueso Cc: Christophe JAILLET Cc: Jann Horn Signed-off-by: Andrew Morton --- ipc/sem.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 00f88aa01ac5..a39cdc7bf88f 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);