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 <[email protected]>
> ---
> 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.
Since Kees already took this patch, I can just patch this in my series if
Kees and you are Ok with this suggestion.
Sorry for the delay in my RFC series, I just got back from paternity leave
and I'm catching up with email.
thanks,
- Joel
> }
> } 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;
On Tue, Oct 30, 2018 at 2:38 PM, Joel Fernandes <[email protected]> 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 <[email protected]>
>> ---
>> 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
> Sorry for the delay in my RFC series, I just got back from paternity leave
> and I'm catching up with email.
No worries! It's many weeks until the next merge window. :)
--
Kees Cook
On Tue, Oct 30, 2018 at 02:52:43PM -0700, Kees Cook wrote:
> On Tue, Oct 30, 2018 at 2:38 PM, Joel Fernandes <[email protected]> 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 <[email protected]>
> >> ---
> >> 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