2014-03-13 0:50 GMT+08:00 Kees Cook <keesc...@chromium.org>:
> On Wed, Mar 12, 2014 at 6:24 AM, Liu Shuo <shuox....@gmail.com> wrote:
>> From: Liu ShuoX <shuox....@intel.com>
>>
>> In case new offset is equal to prz->buffer_size, it won't wrap at this
>> time and will return old(overflow) value next time.
>>
>> Signed-off-by: Liu ShuoX <shuox....@intel.com>
>
> This seems correct; good catch. Have you seen this problem happen, or
> is this just from reading the code?
Thanks.
We indeed hit it when we enhanced the ramoops tracing.
>
> Acked-by: Kees Cook <keesc...@chromium.org>
>
> -Kees
>
>> ---
>> fs/pstore/ram_core.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
>> index de272d4..ff7e3d4 100644
>> --- a/fs/pstore/ram_core.c
>> +++ b/fs/pstore/ram_core.c
>> @@ -54,7 +54,7 @@ static size_t buffer_start_add_atomic(struct
>> persistent_ram_zone *prz, size_t a)
>> do {
>> old = atomic_read(&prz->buffer->start);
>> new = old + a;
>> - while (unlikely(new > prz->buffer_size))
>> + while (unlikely(new >= prz->buffer_size))
>> new -= prz->buffer_size;
>> } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old);
>>
>> @@ -91,7 +91,7 @@ static size_t buffer_start_add_locked(struct
>> persistent_ram_zone *prz, size_t a)
>>
>> old = atomic_read(&prz->buffer->start);
>> new = old + a;
>> - while (unlikely(new > prz->buffer_size))
>> + while (unlikely(new >= prz->buffer_size))
>> new -= prz->buffer_size;
>> atomic_set(&prz->buffer->start, new);
>>
>> --
>> 1.8.3.2
>>
>>
>>
>
>
>
> --
> Kees Cook
> Chrome OS Security
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