From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasily Averin Subject: [PATCH v2 1/2] ipc sem: use kvmalloc for sem_undo allocation Date: Wed, 28 Apr 2021 10:35:15 +0300 Message-ID: References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=virtuozzo.com; s=relay; h=Content-Type:MIME-Version:Date:Message-ID:Subject :From; bh=Eq3YkHGrWHoEc1JLGJOu91L/CKO4jfb0ldrg7T9H29U=; b=GXT/0ycvBaenexct6A/ 9qeKqyR/n2KKbiLtRCVPDsNIHlopmwc132hAQp7Fm2cq8uFCgQdDtrCg+OwtqKWNYLckIXiZf0nnU 2uLYxRw9j0jKZamEGAV9zyVYbqOE9Y0cwgpo5Krb5DvaajQImCXUZOvBxOBM40Ow8C+e14WqzAE= In-Reply-To: Content-Language: en-US List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko , cgroups@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Alexey Dobriyan , Shakeel Butt , Johannes Weiner , Vladimir Davydov , Andrew Morton , Dmitry Safonov <0x7f454c46@gmail.com> size of sem_undo can exceed one page and with the maximum possible nsems = 32000 it can grow up to 64Kb. Let's switch its allocation to kvmalloc to avoid user-triggered disruptive actions like OOM killer in case of high-order memory shortage. User triggerable high order allocations are quite a problem on heavily fragmented systems. They can be a DoS vector. Signed-off-by: Vasily Averin Acked-by: Michal Hocko Reviewed-by: Shakeel Butt Acked-by: Roman Gushchin --- ipc/sem.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 52a6599..93088d6 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -1152,7 +1152,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) un->semid = -1; list_del_rcu(&un->list_proc); spin_unlock(&un->ulp->lock); - kfree_rcu(un, rcu); + kvfree_rcu(un, rcu); } /* Wake up all pending processes and let them fail with EIDRM. */ @@ -1935,7 +1935,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) rcu_read_unlock(); /* step 2: allocate new undo structure */ - new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, + new = kvzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL_ACCOUNT); if (!new) { ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); @@ -1948,7 +1948,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) if (!ipc_valid_object(&sma->sem_perm)) { sem_unlock(sma, -1); rcu_read_unlock(); - kfree(new); + kvfree(new); un = ERR_PTR(-EIDRM); goto out; } @@ -1959,7 +1959,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) */ un = lookup_undo(ulp, semid); if (un) { - kfree(new); + kvfree(new); goto success; } /* step 5: initialize & link new undo structure */ @@ -2420,7 +2420,7 @@ void exit_sem(struct task_struct *tsk) rcu_read_unlock(); wake_up_q(&wake_q); - kfree_rcu(un, rcu); + kvfree_rcu(un, rcu); } kfree(ulp); } -- 1.8.3.1