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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 35AB110002E X-Rspamd-Server: rspam01 X-Stat-Signature: mmgu8zck7xy63j4ggs6bfgwo3twap4z3 X-HE-Tag: 1676300692-63606 X-HE-Meta: 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 U0XhmhmG GqOqLXwWq0ZEW7j3hCpviYk269zB/7nIr55zRV5QC1P1Ycle7NlPkcmJQctFz0ySWWzh/aRDb4or9BdNuvCBWsdU5Jg8A2VCCtjmfdD/ytpuEv4PJ/1ooeBedT9tRrB212uKR18hfNrmZKWPJHFPVrOpI3dPKfxPdsqUmH2x20bFQ8Is1X4JckmnTbkkGPv+AjN7aAstUV3npsRp5LjaTJ68XvN88N1bYcLZWmXpnNa1UVlgUZeVZ5tl7J6IPxD5K7lWsljHQJNv6fiiD3f1ixHFP6FfwLHcg3m3jkbVdJdYiClAJbb86xxjdKHwmyZgP3lv++jwdR0nFfvA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi David, Thank you for quick review! On 2/13/23 4:44 PM, David Hildenbrand wrote: > On 13.02.23 11:43, Muhammad Usama Anjum wrote: >> mwriteprotect_range() errors out if [start, end) doesn't fall in one >> VMA. We are facing a use case where multiple VMAs are present in one >> range of interest. For example, the following pseudocode reproduces the >> error which we are trying to fix: >> >> - Allocate memory of size 16 pages with PROT_NONE with mmap >> - Register userfaultfd >> - Change protection of the first half (1 to 8 pages) of memory to >>    PROT_READ | PROT_WRITE. This breaks the memory area in two VMAs. >> - Now UFFDIO_WRITEPROTECT_MODE_WP on the whole memory of 16 pages errors >>    out. >> >> This is a simple use case where user may or may not know if the memory >> area has been divided into multiple VMAs. >> >> Reported-by: Paul Gofman >> Signed-off-by: Muhammad Usama Anjum >> --- >>   mm/userfaultfd.c | 36 +++++++++++++++++++----------------- >>   1 file changed, 19 insertions(+), 17 deletions(-) >> >> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c >> index 65ad172add27..46e0a014af68 100644 >> --- a/mm/userfaultfd.c >> +++ b/mm/userfaultfd.c >> @@ -738,9 +738,11 @@ int mwriteprotect_range(struct mm_struct *dst_mm, >> unsigned long start, >>               unsigned long len, bool enable_wp, >>               atomic_t *mmap_changing) >>   { >> +    unsigned long end = start + len; >>       struct vm_area_struct *dst_vma; >>       unsigned long page_mask; >>       int err; >> +    VMA_ITERATOR(vmi, dst_mm, start); >>         /* >>        * Sanitize the command parameters: >> @@ -762,26 +764,26 @@ int mwriteprotect_range(struct mm_struct *dst_mm, >> unsigned long start, >>       if (mmap_changing && atomic_read(mmap_changing)) >>           goto out_unlock; >>   -    err = -ENOENT; >> -    dst_vma = find_dst_vma(dst_mm, start, len); >> - >> -    if (!dst_vma) >> -        goto out_unlock; >> -    if (!userfaultfd_wp(dst_vma)) >> -        goto out_unlock; >> -    if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) >> -        goto out_unlock; >> +    for_each_vma_range(vmi, dst_vma, end) { >> +        err = -ENOENT; >>   -    if (is_vm_hugetlb_page(dst_vma)) { >> -        err = -EINVAL; >> -        page_mask = vma_kernel_pagesize(dst_vma) - 1; >> -        if ((start & page_mask) || (len & page_mask)) >> -            goto out_unlock; >> -    } >> +        if (!dst_vma->vm_userfaultfd_ctx.ctx) >> +            break; >> +        if (!userfaultfd_wp(dst_vma)) >> +            break; >> +        if (!vma_can_userfault(dst_vma, dst_vma->vm_flags)) >> +            break; >>   -    uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); >> +        if (is_vm_hugetlb_page(dst_vma)) { >> +            err = -EINVAL; >> +            page_mask = vma_kernel_pagesize(dst_vma) - 1; >> +            if ((start & page_mask) || (len & page_mask)) >> +                break; >> +        } >>   -    err = 0; >> +        uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); > > I suspect you should be adjusting the range to only cover that specific VMA > here. Sorry, you are right. I don't know why it is still working with the blunder. Will send a v2. Thanks, Usama -- BR, Muhammad Usama Anjum