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[209.85.161.52]) by smtp.gmail.com with ESMTPSA id z11-v6sm7291402ywl.36.2018.10.30.14.22.00 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Oct 2018 14:22:01 -0700 (PDT) Received: by mail-yw1-f52.google.com with SMTP id k6-v6so1188947ywa.11 for ; Tue, 30 Oct 2018 14:22:00 -0700 (PDT) X-Received: by 2002:a81:9b83:: with SMTP id s125-v6mr420345ywg.47.1540934520178; Tue, 30 Oct 2018 14:22:00 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a25:3990:0:0:0:0:0 with HTTP; Tue, 30 Oct 2018 14:21:59 -0700 (PDT) In-Reply-To: <20181030075234.21137-1-wangpeng15@xiaomi.com> References: <20181030075234.21137-1-wangpeng15@xiaomi.com> From: Kees Cook Date: Tue, 30 Oct 2018 14:21:59 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap() To: Peng Wang Cc: Anton Vorontsov , Colin Cross , Tony Luck , Joel Fernandes , LKML , vipwangerxiao@gmail.com Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 30, 2018 at 12:52 AM, Peng Wang wrote: > When initialing prz with invalid data in buffer(no PERSISTENT_RAM_SIG), > function call path is like this: > > ramoops_init_prz -> > | > |-> persistent_ram_new -> persistent_ram_post_init -> persistent_ram_zap > | > |-> persistent_ram_zap > > As we can see, persistent_ram_zap() is called twice. > We can avoid this by adding an option to persistent_ram_new(), and > only call persistent_ram_zap() when it is needed. > > Signed-off-by: Peng Wang Thanks! I've applied this to my devel branch. I'll have it in linux-next once -rc2 lands. -Kees > --- > fs/pstore/ram.c | 4 +--- > fs/pstore/ram_core.c | 5 +++-- > include/linux/pstore_ram.h | 1 + > 3 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c > index ffcff6516e89..b51901f97dc2 100644 > --- a/fs/pstore/ram.c > +++ b/fs/pstore/ram.c > @@ -640,7 +640,7 @@ static int ramoops_init_prz(const char *name, > > label = kasprintf(GFP_KERNEL, "ramoops:%s", name); > *prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info, > - cxt->memtype, 0, label); > + cxt->memtype, PRZ_FLAG_ZAP_OLD, label); > if (IS_ERR(*prz)) { > int err = PTR_ERR(*prz); > > @@ -649,8 +649,6 @@ static int ramoops_init_prz(const char *name, > return err; > } > > - persistent_ram_zap(*prz); > - > *paddr += sz; > > return 0; > diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c > index 12e21f789194..2ededd1ea1c2 100644 > --- a/fs/pstore/ram_core.c > +++ b/fs/pstore/ram_core.c > @@ -505,15 +505,16 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, > pr_debug("found existing buffer, size %zu, start %zu\n", > buffer_size(prz), buffer_start(prz)); > persistent_ram_save_old(prz); > - return 0; > + if (!(prz->flags & PRZ_FLAG_ZAP_OLD)) > + return 0; > } > } else { > pr_debug("no valid data in buffer (sig = 0x%08x)\n", > prz->buffer->sig); > + prz->buffer->sig = sig; > } > > /* Rewind missing or invalid memory area. */ > - prz->buffer->sig = sig; > persistent_ram_zap(prz); > > return 0; > diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h > index 602d64725222..6e94980357d2 100644 > --- a/include/linux/pstore_ram.h > +++ b/include/linux/pstore_ram.h > @@ -30,6 +30,7 @@ > * PRZ_FLAG_NO_LOCK is used. For all other cases, locking is required. > */ > #define PRZ_FLAG_NO_LOCK BIT(0) > +#define PRZ_FLAG_ZAP_OLD BIT(1) > > struct persistent_ram_buffer; > struct rs_control; > -- > 2.19.1 > -- Kees Cook