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=1794437719; b=oN8kGZg9qrCmRkkpqGeSloKpKnxaNl/MZSwOuCi8XKzenGQTP9WFy8dL4xGs8ZpKRZLa Hb8cJRYih/MbSSMDmNyylYzzCWX4pHeUtL1l/9HNFQisIzM3Bhu3zRuCnIk7bH+PhfppO tCSn+XsaRfOyWonQ/lcHUBo9awiGdbjQqItAZkoXJlJrmc25Xta2u5DhJ9jcz9YJYZkkm DSm8WpYmkmRaxA3V9EXhcpGVRVX6cE4j8pbrL8uRTAQbyrHx2btWlSic/xcW3Sx1EJtac nm2Mi5LV59QASWOg4P8exMIVYYECvqwBxqmSbT0z8RG/T0mF353F0KMPnHv62PH6xTQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794437719; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=1gdf9Bq6jlJ/Em8YXNZn+PhSzP7XddBcL4qXg1rgFGs=; b=P8u7SpGSZMaZH43dXpycRXMTll8zYIPjk0GVfUwdTLlhTuUNBjaAt7jjFopMkEH/+D9u qZ+eGk1N0Xl4L+HfV1StMy10xMICd9QeDuc/FykqRkX6B7BY54qjjMzEjEbPjHesjBDSP evrVe2ov+90Y6BITSk7/3N7vuRW38UPHlI0qexagGNv5+HA3kuA+QdpOWtOAjwZkbX1LW T18sjAHElftUXaIetVGT8h6OB0dSq4aX+uXRenEHARObRTBpo9c9/u1uA8cefZji3S/BT WZzsy0gHf5E6eaNw6GqWewi7f+FHoTa7UExep5Szmskd/XCT+CAriTHmiZHPEmI/PjA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Oy5NH1hS; 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 0B3D3606A31C for ; Wed, 11 Nov 2026 22:55:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Oy5NH1hS Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C0221F00A05; Wed, 11 Nov 2026 22:55:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794437718; bh=1gdf9Bq6jlJ/Em8YXNZn+PhSzP7XddBcL4qXg1rgFGs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Oy5NH1hSiBF8Q8rG86XY878Qbqwqwf7RQTl7C5TBLEd9SORpohB+s7FM9isTGuIgQ hcrEhDkw57tBtA14HeKPpRW0EL6WLsUgCL3yjr5Lvmx9wiwvQHqQh3m5fbKlanU1Wi snOLU+59dY7aa7TDQxj274YTRZpEnsfyz56MReDyUpeXbNy6NUklduRQ4Rs3+PqxRs ZMDBxiac+EZzMFEAh95zojrt+tgK+tMhsH2a6CNvFLys+g+4/aevlOjR1hTHEQf4R6 n8Q5FKmxAPWrhZlcGmyw3C7T22fusjEEVAqqjumZqquU8xhJFAFqqXExZ3wkirw/BB TySBSAjmakQ0A== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , "Gregory Price (Meta)" , "Mike Rapoport (Microsoft)" , "Lorenzo Stoakes (ARM)" , Muhammad Usama Anjum , Sasha Levin Subject: [PATCH 7.3.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 17:55:16 -0500 Message-ID: <20261111225453.188656-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200156-failed-7.3-4eee9c389b07@kernel.org> References: <20261109200156-failed-7.3-4eee9c389b07@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit 4eee9c389b072e161549d46dcb1ae10b0222717e ] UFFDIO_REGISTER can replace MISSING or MINOR tracking without waking faults that are already queued. For example, switching an anonymous range from MISSING to WP leaves a missing-fault waiter asleep until userspace explicitly wakes it. When a registration change removes a UFFD mode, wake waiters in the affected interval after updating the VMA. The VMA is write-locked at this point, so no new faults can queue under the old modes and woken threads cannot retry until mmap_write_unlock(). Waiters for retained modes in the same interval may also wake and refault. The hang reproduces for MISSING-to-WP and MINOR-to-MISSING transitions, with both read and unread fault events. Fixes: 63b2d4174c4a ("userfaultfd: wp: add the writeprotect API to userfaultfd ioctl") Cc: stable@vger.kernel.org Reviewed-by: Gregory Price (Meta) Tested-by: Gregory Price (Meta) Signed-off-by: Gregory Price (Meta) Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Lorenzo Stoakes (ARM) Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-25-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) [ sashal: Adjusted context to retain is_vm_hugetlb_page() instead of vma_is_hugetlb(). ] Signed-off-by: Sasha Levin --- mm/userfaultfd.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index cc37b60fc3e81..d94ca9d8a9d5f 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2287,6 +2287,9 @@ static struct vm_area_struct *userfaultfd_clear_vma(struct vma_iterator *vmi, return ret; } +static void wake_userfault_range(struct userfaultfd_ctx *ctx, + unsigned long start, unsigned long end); + /* Assumes mmap write lock taken, and mm_struct pinned. */ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, struct vm_area_struct *vma, @@ -2304,6 +2307,8 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, prev = vma; for_each_vma_range(vmi, vma, end) { + const bool any_mode_removed = vma->vm_flags & __VM_UFFD_FLAGS & ~vm_flags; + cond_resched(); VM_WARN_ON_ONCE(!vma_can_userfault(vma, vm_flags, wp_async)); @@ -2349,6 +2354,10 @@ static int userfaultfd_register_range(struct userfaultfd_ctx *ctx, */ userfaultfd_set_ctx(vma, ctx, vm_flags); + /* Retry faults for removed modes while the VMA is write-locked. */ + if (any_mode_removed) + wake_userfault_range(ctx, start, vma_end); + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); @@ -3665,6 +3674,17 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, __wake_userfault(ctx, range); } +static void wake_userfault_range(struct userfaultfd_ctx *ctx, + unsigned long start, unsigned long end) +{ + struct userfaultfd_wake_range range = { + .start = start, + .len = end - start, + }; + + wake_userfault(ctx, &range); +} + static __always_inline int validate_unaligned_range( struct mm_struct *mm, __u64 start, __u64 len) { -- 2.53.0