Messages in this thread | | | From | Peng15 Wang 王鹏 <> | Subject | Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap() | Date | Wed, 31 Oct 2018 03:57:51 +0000 |
| |
>From: Joel Fernandes <joel@joelfernandes.org> >Sent: Wednesday, October 31, 2018 6:16 >To: Kees Cook >Cc: Peng15 Wang 王鹏; Anton Vorontsov; Colin Cross; Tony Luck; LKML; vipwangerxiao@gmail.com >Subject: Re: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap() > >On Tue, Oct 30, 2018 at 02:52:43PM -0700, Kees Cook wrote: >> On Tue, Oct 30, 2018 at 2:38 PM, Joel Fernandes <joel@joelfernandes.org> wrote: >> > On Tue, Oct 30, 2018 at 03:52:34PM +0800, 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 <wangpeng15@xiaomi.com> >> >> --- >> >> 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); >> > >> > Looks good to me except the minor comment below: >> > >> >> >> >> @@ -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; >> > >> > This could be written differently. >> > >> > We could just do: >> > >> > if (prz->flags & PRZ_FLAG_ZAP_OLD) >> > persistent_ram_zap(prz); >> > >> > And remove the zap from below below. >> >> I actually rearranged things a little to avoid additional round-trips >> on the mailing list. :) >> >> > Since Kees already took this patch, I can just patch this in my series if >> > Kees and you are Ok with this suggestion. >> >> I've put it up here: >> https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=pstore/devel&id=ac564e023248e3f4d87917b91d12376ddfca5000 > >Cool, it LGTM :) > >- Joel >
Thank you all for these warm help.
This is my first time to submit a patch to community. Feel great!
| |