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[34.127.76.238]) by smtp.gmail.com with ESMTPSA id m3-20020a17090a2c0300b001f021cdd73dsm1851984pjd.10.2022.08.10.09.27.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Aug 2022 09:27:15 -0700 (PDT) Date: Wed, 10 Aug 2022 16:27:11 +0000 From: Carlos Llamas To: Liam Howlett Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , syzbot , Andrew Morton , Ondrej Mosnacek , "syzkaller-bugs@googlegroups.com" , Minchan Kim , Christian Brauner , Greg Kroah-Hartman , Hridya Valsaraju , Joel Fernandes , Martijn Coenen , Suren Baghdasaryan , Todd Kjos , Matthew Wilcox , Arve =?iso-8859-1?B?SGr4bm5lduVn?= Subject: Re: [PATCH v2] binder_alloc: Add missing mmap_lock calls when using the VMA Message-ID: References: <20220810160209.1630707-1-Liam.Howlett@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220810160209.1630707-1-Liam.Howlett@oracle.com> ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=GVeX1RfP; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf29.hostedemail.com: domain of cmllamas@google.com designates 209.85.210.177 as permitted sender) smtp.mailfrom=cmllamas@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660148837; a=rsa-sha256; cv=none; b=58EWgEhQTLoz9uHl8qpb7nUnIUZbps8crpnMx/vPclsaxLWDDyN/3vNFiNb6EziGgN+Wp+ w8WfeS2gQZQA+Cn/BorgvmKLgu5t8nk+zB4mDNPb87ym6OYSGXh6vRP0/Dii/kLPh2mE2T +qlROPsRFsjaFGhfAVLksAuH4rQAiN8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660148837; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=iaOXFsKF+VEOO1NtlLaIlaeLAxiEe5HdvjUlYcOWT3Q=; b=kPyNmlr/NnjMWYQbmP2k4Ve5Wwg3/xnpNHhWonyWqO45zNTN6GFQsjbrLqH8Z5ITqG8/PO yfo16XU3hGpG1fCzs/bfrWziQBMPIrArfMMfyHCLlKmT66NKOUK1hRlsehBfh8epCH7w+B pker46YPGQowgKXQX1Lhx23/qbAu/zk= X-Rspamd-Server: rspam10 X-Rspam-User: Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=GVeX1RfP; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf29.hostedemail.com: domain of cmllamas@google.com designates 209.85.210.177 as permitted sender) smtp.mailfrom=cmllamas@google.com X-Rspamd-Queue-Id: 8E59A12006A X-Stat-Signature: 1qzjqy6ckuj5qkffdx56ard1f9knnr1r X-HE-Tag: 1660148837-734729 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 10, 2022 at 04:02:25PM +0000, Liam Howlett wrote: > Take the mmap_read_lock() when using the VMA in > binder_alloc_print_pages() and when checking for a VMA in > binder_alloc_new_buf_locked(). > > It is worth noting binder_alloc_new_buf_locked() drops the VMA read lock > after it verifies a VMA exists, but may be taken again deeper in the > call stack, if necessary. > > Reported-by: Ondrej Mosnacek > Reported-by: syzbot+a7b60a176ec13cafb793@syzkaller.appspotmail.com > Fixes: a43cfc87caaf (android: binder: stop saving a pointer to the VMA) > Signed-off-by: Liam R. Howlett > --- > drivers/android/binder_alloc.c | 31 +++++++++++++++++++++---------- > 1 file changed, 21 insertions(+), 10 deletions(-) > > diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c > index f555eebceef6..c5e7c6d3a844 100644 > --- a/drivers/android/binder_alloc.c > +++ b/drivers/android/binder_alloc.c > @@ -395,12 +395,15 @@ static struct binder_buffer *binder_alloc_new_buf_locked( > size_t size, data_offsets_size; > int ret; > > + mmap_read_lock(alloc->vma_vm_mm); > if (!binder_alloc_get_vma(alloc)) { > + mmap_read_unlock(alloc->vma_vm_mm); > binder_alloc_debug(BINDER_DEBUG_USER_ERROR, > "%d: binder_alloc_buf, no vma\n", > alloc->pid); > return ERR_PTR(-ESRCH); > } > + mmap_read_unlock(alloc->vma_vm_mm); > > data_offsets_size = ALIGN(data_size, sizeof(void *)) + > ALIGN(offsets_size, sizeof(void *)); > @@ -922,17 +925,25 @@ void binder_alloc_print_pages(struct seq_file *m, > * Make sure the binder_alloc is fully initialized, otherwise we might > * read inconsistent state. > */ > - if (binder_alloc_get_vma(alloc) != NULL) { > - for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { > - page = &alloc->pages[i]; > - if (!page->page_ptr) > - free++; > - else if (list_empty(&page->lru)) > - active++; > - else > - lru++; > - } > + > + mmap_read_lock(alloc->vma_vm_mm); > + if (binder_alloc_get_vma(alloc) == NULL) { > + mmap_read_unlock(alloc->vma_vm_mm); > + goto uninitialized; > } > + > + mmap_read_unlock(alloc->vma_vm_mm); > + for (i = 0; i < alloc->buffer_size / PAGE_SIZE; i++) { > + page = &alloc->pages[i]; > + if (!page->page_ptr) > + free++; > + else if (list_empty(&page->lru)) > + active++; > + else > + lru++; > + } > + > +uninitialized: > mutex_unlock(&alloc->mutex); > seq_printf(m, " pages: %d:%d:%d\n", active, lru, free); > seq_printf(m, " pages high watermark: %zu\n", alloc->pages_high); > -- > 2.35.1 Thanks Liam, this looks good. Acked-by: Carlos Llamas