From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 6D3EF6B0253 for ; Mon, 23 May 2016 18:14:04 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id 129so216432257pfx.0 for ; Mon, 23 May 2016 15:14:04 -0700 (PDT) Received: from mail-pf0-x241.google.com (mail-pf0-x241.google.com. [2607:f8b0:400e:c00::241]) by mx.google.com with ESMTPS id g82si8424414pfj.143.2016.05.23.15.14.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 23 May 2016 15:14:03 -0700 (PDT) Received: by mail-pf0-x241.google.com with SMTP id 145so20267340pfz.1 for ; Mon, 23 May 2016 15:14:03 -0700 (PDT) Date: Mon, 23 May 2016 15:13:58 -0700 From: Alexei Starovoitov Subject: Re: bpf: use-after-free in array_map_alloc Message-ID: <20160523221356.GA35044@ast-mbp.thefacebook.com> References: <5713C0AD.3020102@oracle.com> <20160417172943.GA83672@ast-mbp.thefacebook.com> <5742F127.6080000@suse.cz> <5742F267.3000309@suse.cz> <20160523213501.GA5383@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160523213501.GA5383@mtj.duckdns.org> Sender: owner-linux-mm@kvack.org List-ID: To: Tejun Heo Cc: Vlastimil Babka , Sasha Levin , ast@kernel.org, "netdev@vger.kernel.org" , LKML , Christoph Lameter , Linux-MM layout , Marco Grassi , Daniel Borkmann On Mon, May 23, 2016 at 05:35:01PM -0400, Tejun Heo wrote: > Hello, > > Can you please test whether this patch resolves the issue? While > adding support for atomic allocations, I reduced alloc_mutex covered > region too much. after the patch the use-after-free is no longer seen. Tested-by: Alexei Starovoitov > > Thanks. > > diff --git a/mm/percpu.c b/mm/percpu.c > index 0c59684..bd2df70 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -162,7 +162,7 @@ static struct pcpu_chunk *pcpu_reserved_chunk; > static int pcpu_reserved_chunk_limit; > > static DEFINE_SPINLOCK(pcpu_lock); /* all internal data structures */ > -static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop */ > +static DEFINE_MUTEX(pcpu_alloc_mutex); /* chunk create/destroy, [de]pop, map extension */ > > static struct list_head *pcpu_slot __read_mostly; /* chunk list slots */ > > @@ -435,6 +435,8 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc) > size_t old_size = 0, new_size = new_alloc * sizeof(new[0]); > unsigned long flags; > > + lockdep_assert_held(&pcpu_alloc_mutex); > + > new = pcpu_mem_zalloc(new_size); > if (!new) > return -ENOMEM; > @@ -895,6 +897,9 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > return NULL; > } > > + if (!is_atomic) > + mutex_lock(&pcpu_alloc_mutex); > + > spin_lock_irqsave(&pcpu_lock, flags); > > /* serve reserved allocations from the reserved chunk if available */ > @@ -967,12 +972,11 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > if (is_atomic) > goto fail; > > - mutex_lock(&pcpu_alloc_mutex); > + lockdep_assert_held(&pcpu_alloc_mutex); > > if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) { > chunk = pcpu_create_chunk(); > if (!chunk) { > - mutex_unlock(&pcpu_alloc_mutex); > err = "failed to allocate new chunk"; > goto fail; > } > @@ -983,7 +987,6 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > spin_lock_irqsave(&pcpu_lock, flags); > } > > - mutex_unlock(&pcpu_alloc_mutex); > goto restart; > > area_found: > @@ -993,8 +996,6 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > if (!is_atomic) { > int page_start, page_end, rs, re; > > - mutex_lock(&pcpu_alloc_mutex); > - > page_start = PFN_DOWN(off); > page_end = PFN_UP(off + size); > > @@ -1005,7 +1006,6 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > > spin_lock_irqsave(&pcpu_lock, flags); > if (ret) { > - mutex_unlock(&pcpu_alloc_mutex); > pcpu_free_area(chunk, off, &occ_pages); > err = "failed to populate"; > goto fail_unlock; > @@ -1045,6 +1045,8 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, > /* see the flag handling in pcpu_blance_workfn() */ > pcpu_atomic_alloc_failed = true; > pcpu_schedule_balance_work(); > + } else { > + mutex_unlock(&pcpu_alloc_mutex); > } > return NULL; > } > @@ -1137,6 +1139,8 @@ static void pcpu_balance_workfn(struct work_struct *work) > list_for_each_entry_safe(chunk, next, &to_free, list) { > int rs, re; > > + cancel_work_sync(&chunk->map_extend_work); > + > pcpu_for_each_pop_region(chunk, rs, re, 0, pcpu_unit_pages) { > pcpu_depopulate_chunk(chunk, rs, re); > spin_lock_irq(&pcpu_lock); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org