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SubjectRe: [PATCH v4] pstore: Avoid duplicate call of persistent_ram_zap()
On Tue, Oct 30, 2018 at 12:52 AM, Peng Wang <wangpeng15@xiaomi.com> 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>

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

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