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Mon, 13 Feb 2023 16:31:40 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1676305902; bh=OiTcyrHZ0v3oC/V7QnPlyQu3zF7d7MV1OS0jVwPURZU=; h=From:To:Cc:Subject:Date:From; b=Uc3zOm2nBYWIjJv2z1Is850ACuGzKXcoqliy3ugB5rRc28XwAUkhcyLgGezS62dNw vWsv8rsKCEB+V4zQOzvteoxgT//NwYQ0BSlVzV+dNnOuwp3otEQWzbiqnKHRbCei/l osOICLKHWG29ijdU4Rha4hg7tq/Nsk9r4mTZYSajGQHnlqDVWh55D5mYB0OJxHdvyQ 52yFWnOTgus4Nstl0Iva3Mw9bUSYhyjz6m2SCf2qRMXT8PFb3UdY8LyrOO3cS9SERP xyelRMHwlM9SbA5h+7MCpehfW5a8HWQyrDx/zZFw9cNC9TKcjWFgK/J3+sc6gVMZcn +5VpNA5l3YPxQ== From: Muhammad Usama Anjum To: peterx@redhat.com, david@redhat.com, Andrew Morton Cc: Muhammad Usama Anjum , kernel@collabora.com, Paul Gofman , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] mm/userfaultfd: Support WP on multiple VMAs Date: Mon, 13 Feb 2023 21:31:23 +0500 Message-Id: <20230213163124.2850816-1-usama.anjum@collabora.com> X-Mailer: git-send-email 2.39.1 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 79B9C4002A X-Stat-Signature: j4ro4fuiftrho7ze3qwsoh69ouf8kd8i X-HE-Tag: 1676305904-292394 X-HE-Meta: U2FsdGVkX19DkaCv8VXbgBUG6a9oP5l8iFCkOHqhCO/3/epuMJEqOZE6t+7YBKkh8NDCjnvTH074tRT6+LpN58DrhofOKlyMGV6y2W3R3uRtGwJaZ4Y0nUGdTDdNpJHfK3tN/EK3lYaHvGFkz2m4ESGSEVDSSMgcyFKK9v0dw/DkexRJfXplX6sl5X1bvKnXWqag87O444e3LB7yBUXCfnu5atWY9BuURTUVMbJq0Zs4iRZ4opDGZxI6Zq97MvZDHVNHEg7+YtqzLKejE2GfSoNhjb3ojLg0A3EiPtWKjDSNGa2zDQ5zKIH5veyLkksS6ZAsR33kCJB5iQ1tUXJuwc7iy2+DqEeT5eKTIWLart34e9hTBR3sMtUGXv6CZIk0FzbdaJlZt6CvSslPVjlLzpCXDgbBnYtIof5jHtSEWYpE0OhFaPSnPBm/aXEl3LnqJSRgNSDWityu0qAjUlSp1CpIqIs0U3YeogxmEOcauGIm5e3gYfOOzl3EWMmods26bQHfJ55vZgBu/aBmjmjBQ+yseShrlZna3yU2/2S0YYwfJVZjkO5utA8nFyLvmHoSuoUcGL2aChU96Z+5sOsbgFAiDF23WyWJd2E6RKBeXJ35DI1hLW2ZQq9uefVco6BzD2TihwCLwVMKW5RmeN+zzLO5yrWTZnzl+lzyV9mfglPquWyMO6PoHW0N+i57uimkW7HFujIHsrlZrEBZCtmNB2fi7h72pPTRVq5NWp2mf39oDMMmERwkmNh0iAYvSmoKS7jlNn3LtaAuXV/G9k159CxrX75FZhCFWbAAvZxcR75z/rSfg9/f67K9nl9YyPhj/LoEqIoCfvwq6jdj2uRLOsIZjga3Xo/JZa5Y7nTZxdtfNeHn60KyazwKwOsuKVw18Dju/wSzMMiB4ZHtZ4nZWPCwHErNdNNL0riwOcvkMBtL/npWL643MIeFOsTkqIAd46PlzbWXDIPTfdDrrz4 nNq06sS7 T8GjRUDN/Lo3D0ugNrpPn/K8hbatpEAas2cWkubtDpDAA0vF3ymRvPUkHTH4eG2P3fSW7LaQX3eQnB0rWXSenaV630CApniTHb+zC9b0zaVAqgqMTzdXw0MjPp9RFvxwnWrvTVLnd6tflzZ0U42LQ13Ao73guA2ZTwVGCUxBwrALmHybJvTJI/ad3z8Sms/Y/bICJcxrZ/e32YnKu4vN4/zhL/CtVKJIQQK97M7apNoDlNgI21o7g1zvI3I/XZGJ7xETH4gXv5grnmsOLncwXr8PdIEiBpJNDQpcO5TWAWYwhO29PIP7jF0jjqRZhaI6xH30/ 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: 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 --- Changes since v1: - Correct the start and ending values passed to uffd_wp_range() --- mm/userfaultfd.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 65ad172add27..bccea08005a8 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -738,9 +738,12 @@ 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; + unsigned long _start, _end; struct vm_area_struct *dst_vma; unsigned long page_mask; int err; + VMA_ITERATOR(vmi, dst_mm, start); /* * Sanitize the command parameters: @@ -762,26 +765,29 @@ 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); + for_each_vma_range(vmi, dst_vma, end) { + err = -ENOENT; - 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; + 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; - 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 (is_vm_hugetlb_page(dst_vma)) { + err = -EINVAL; + page_mask = vma_kernel_pagesize(dst_vma) - 1; + if ((start & page_mask) || (len & page_mask)) + break; + } - uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp); + _start = (dst_vma->vm_start > start) ? dst_vma->vm_start : start; + _end = (dst_vma->vm_end < end) ? dst_vma->vm_end : end; - err = 0; + uffd_wp_range(dst_mm, dst_vma, _start, _end - _start, enable_wp); + err = 0; + } out_unlock: mmap_read_unlock(dst_mm); return err;