Messages in this thread | ![/](/images/icornerl.gif) | | From | Michał Mirosław <> | Date | Wed, 21 Jun 2023 15:29:20 +0200 | Subject | Re: [PATCH v19 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs |
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On Wed, 21 Jun 2023 at 08:35, Muhammad Usama Anjum <usama.anjum@collabora.com> wrote: > On 6/20/23 11:03 PM, Andrei Vagin wrote: > ... > >> +struct pagemap_scan_private { > >> + struct page_region *vec_buf, cur_buf; > >> + unsigned long long vec_buf_len, vec_buf_index, max_pages, found_pages, flags; > > > > should it be just unsigned long? > These internal values are storing data coming from user in struct > pm_scan_arg in which all variables are 64 bit(__u64) explicitly. This is > why we have unsigned long long here. It is absolutely necessary.
vec_buf_len and vec_buf_index can only have values in 0..512 range. flags has only a few lower bits defined (this is checked on ioctl entry) and max_pages can be limited to ULONG_MAX. Actually putting `if (!max_pages || max_pages > ULONG_MAX) max_pages = ULONG_MAX` would avoid having to check !max_pages during the walk.
Best Regards Michał Mirosław
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