From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794293131; b=alC0+jNgmWF+V0BswVvcqnoIVn00CPHaW/AbxWf7jSBffhEYiURr6wEFA4x3mTTbaGQE 9XHHu+mx5B8kK/dIdbE8FqWN/IzHL/zSjFZTKlaCGvnWVzcpV8dy0Z+Ny9PNXrrlW0ccC CB0Z/JDYW88CmICDyrAaJUowFc6pmQC8axERfbO7KMGg9ZED2JWJXOI/J2BRBaiReZz3V 6AmyUQ3md8tl84TyoO5jMsLcUAMmLj1HXh6xgmhF3L8C3/7k3TcTvaqEFn0HtDrsScD2k pRgXTVmpyYBixzFEzya5okCRMj1+g8YM7LZZTnC2b1ZrfPjsXPJUywpu3k55mVJVA4w== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794293131; h=Received:DKIM-Signature:Date:To:From:Subject:Message-Id; bh=atKKCDUPvmRNBnqZo/JGr1sKPs4dlxQ1gPDFpmJarr4=; b=08sMWi6p6GJIqTXnMupBWPjIfLbwUOm34T00UA+EATtYsdY2FOm7eV4mz2XBUQY/VBul gllHZg/Ft14Ju3eO0zI/AC43hcWgS0N+t2NoU4C2EhAdud/f4aKpY/7CLUCIFqWCaZQ3q uXu51gdLU8OeQYjNXkm55C2o0/b6Mu/ccsXKQVS97weaQURAUfdkT0E0c+VHa1Uruxi0R QNJbQXrQ2anY77O+0+s+NYkvriCHCAsgAH51AsJ5qvxvpKODYR5hfnHYGgLzdjUX1xoIh TeDMBDvIujANGM4P11+eAulhbgt/GpGCZ13VRyNk8lSvv/X/Q4eC4JMHR5luiUhuDew== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=JhpyT3OO; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A966E606CB24; Tue, 10 Nov 2026 06:45:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.a=rsa-sha256 header.s=korg header.b=JhpyT3OO Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C39F1F008A4; Tue, 10 Nov 2026 06:45:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1794293130; bh=atKKCDUPvmRNBnqZo/JGr1sKPs4dlxQ1gPDFpmJarr4=; h=Date:To:From:Subject; b=JhpyT3OOx1J7v5pqOA9HdtZyMp39ZXHL8+cDJT4Ii+PCkWBsBjQZ+S8SGOe+UnnV3 tTEiG2oHoZng1mVfuxd9z3AAsMAo8KxKhsgcjmIwNq5i1v7s7m6NDsaZOz+wdagWyT K3YJaJOTtAdVTpPLx9Y4DtQRzOHnts7/qGNIsTcE= Date: Mon, 09 Nov 2026 22:45:30 -0800 To: mm-commits@vger.kernel.org,tz2294@columbia.edu,stable@vger.kernel.org, peterx@redhat.com,azpijr@gmail.com,rppt@kernel.org,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] userfaultfd-clear-uffd-state-in-child-ptes-if-uffd-is-released-during-fork.patch removed from -mm tree Message-Id: <20261110064530.6C39F1F008A4@smtp.kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list The quilt patch titled Subject: userfaultfd: clear uffd state in child PTEs if uffd is released during fork has been removed from the -mm tree. Its filename was userfaultfd-clear-uffd-state-in-child-ptes-if-uffd-is-released-during-fork.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: "Mike Rapoport (Microsoft)" Subject: userfaultfd: clear uffd state in child PTEs if uffd is released during fork Date: Sat, 31 Oct 2026 20:14:03 +0200 With UFFD_FEATURE_EVENT_FORK the userfaultfd context is duplicated for the child process, the child VMAs are registered with the new context, and uffd protection state from the parent PTEs is copied into the child. If the parent's userfaultfd is released before the fork event is read, userfaultfd_release_new() resets the VMA flags but keeps uffd state in the child PTEs. This leaves the child's VMAs in an inconsistent state: they are not registered with userfaultfd but their mappings carry uffd protection state. If the child registers the range with userfaultfd again, the stale state turns into protection the child never asked for. When a write fault makes such a PTE writable without copying the page, the uffd bit remains set and page_table_check_pte_flags() warns about it. Split resolving of the uffd PTE state out of userfaultfd_clear_vma() and call it from userfaultfd_release_new() before resetting the VMA. Link: https://lore.kernel.org/20261031-uffd-prot-bits-fork-event-v2-1-c448e57df417@kernel.org Fixes: f369b07c8614 ("mm/uffd: reset write protection when unregister with wp-mode") Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Andrew Morton Reviewed-by: Jose A. Perez de Azpillaga Tested-by: Jose A. Perez de Azpillaga Reviewed-by: Tal Zussman Tested-by: Tal Zussman Cc: Peter Xu Cc: --- mm/userfaultfd.c | 47 ++++++++++++++++++++++++++++----------------- 1 file changed, 30 insertions(+), 17 deletions(-) --- a/mm/userfaultfd.c~userfaultfd-clear-uffd-state-in-child-ptes-if-uffd-is-released-during-fork +++ a/mm/userfaultfd.c @@ -2192,6 +2192,32 @@ static void userfaultfd_reset_ctx(struct userfaultfd_set_ctx(vma, NULL, 0); } +/* + * Clear uffd state from a WP or RWP range: the uffd bit, WP markers and + * RWP PAGE_NONE entries. Call this before dropping the registration, as it + * needs the VMA flags to know what to resolve. + */ +static void userfaultfd_clear_ptes(struct vm_area_struct *vma, + unsigned long start, unsigned long end) +{ + unsigned int mm_cp_flags = 0; + struct mmu_gather tlb; + + if (!userfaultfd_protected(vma)) + return; + + if (userfaultfd_wp(vma)) + mm_cp_flags |= MM_CP_UFFD_WP_RESOLVE; + if (userfaultfd_rwp(vma)) + mm_cp_flags |= MM_CP_UFFD_RWP_RESOLVE; + if (vma_wants_manual_pte_write_upgrade(vma)) + mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; + + tlb_gather_mmu(&tlb, vma->vm_mm); + change_protection(&tlb, vma, start, end, mm_cp_flags); + tlb_finish_mmu(&tlb); +} + static struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi, struct vm_area_struct *prev, struct vm_area_struct *vma, @@ -2211,22 +2237,7 @@ static struct vm_area_struct *userfaultf if (start == vma->vm_start && end == vma->vm_end) give_up_on_oom = true; - /* Clear the uffd bit and/or restore protnone PTEs */ - if (userfaultfd_protected(vma)) { - unsigned int mm_cp_flags = 0; - struct mmu_gather tlb; - - if (userfaultfd_wp(vma)) - mm_cp_flags |= MM_CP_UFFD_WP_RESOLVE; - if (userfaultfd_rwp(vma)) - mm_cp_flags |= MM_CP_UFFD_RWP_RESOLVE; - if (vma_wants_manual_pte_write_upgrade(vma)) - mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE; - - tlb_gather_mmu(&tlb, vma->vm_mm); - change_protection(&tlb, vma, start, end, mm_cp_flags); - tlb_finish_mmu(&tlb); - } + userfaultfd_clear_ptes(vma, start, end); ret = vma_modify_flags_uffd(vmi, prev, vma, start, end, &new_vma_flags, NULL_VM_UFFD_CTX, @@ -2335,8 +2346,10 @@ static void userfaultfd_release_new(stru /* the various vma->vm_userfaultfd_ctx still points to it */ mmap_write_lock(mm); for_each_vma(vmi, vma) { - if (vma->vm_userfaultfd_ctx.ctx == ctx) + if (vma->vm_userfaultfd_ctx.ctx == ctx) { + userfaultfd_clear_ptes(vma, vma->vm_start, vma->vm_end); userfaultfd_reset_ctx(vma); + } } mmap_write_unlock(mm); } _ Patches currently in -mm which might be from rppt@kernel.org are mm-vma-undo-userfaultfd-unmap-preparation-when-unmapping-fails.patch hibernation-make-swsusp_page-helpers-static.patch hibernation-ensure-secretmem-pages-dont-reach-a-snapshot.patch hibernate-handle-potential-errors-in-hibernate_mapunmap_page.patch hibernation-kfence-explicitly-map-unmap-kfence-pages.patch hibernation-make-hibernation-unavailable-when-debug_pagealloc-is-on.patch