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=1793440006; b=BLNrseXaBvozE3fztgHctXBxpD402Grtupyj9gfP/Q0TFeyNtOXryvJ3+J8swj+7NCdj arxDDJMYfyxdzdBd+OBURum2w2rZj+EbOJfjT7PFKAg1/sMSfF1uXmXJELaRsVNevUY4V nKBB2gWOr1VrMkuA8E5YGraVfWBYss6li5Ob5Kdoho/HWCqXyj+xSHxgacdLTvVAMSICD zIyzMIFwMg6NxN3xqYmzgDBqy0NlCZOHVz0j+xDon9UE3aSkxcsVKXa2gliEIRBJCs5hN sUUGx34PEfLfTWckBykrjRHS5B20IhZRrTnqVpxT7ELSwXtPX9lhxMWqYsywqWiTbdA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793440006; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer:X-Developer-Signature:X-Developer-Key; bh=aFAIeNXgFr1JMM5WH77Fc7EqldEyl6IknIX1LhJHwrw=; b=3+1kSPtPdKXDh/Ooek/pip/fStWszriFHrjqD0mw2tZuMJTryVBvTZOScAmGysIvTMMy oD7CwLZCTytm84363RTPyQUzLERzB3uVsvx14O0ji1nTemLNujah9EetOvyvyX8jL5Yks w4mD9hJnwkVhrSj+7IfrI9sOwP4GRHhMGtM6J4xPMHjFwO1xjErbWUI2+SYnlDaLdSx5f tpAnyrS/fxFGVmAhFxeeH3M9dsB4Y6wandCrayBBYenC/A+KbhYuaAxgWBcaE4c6GEvVo xH6gQ4bVHOA16gg+JKnskjlnRh6lgCu9AQ32yAZPz4badktHyjDC2oNjOzj8gVyjBhQ== 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=EX+rzLR3; 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 A1CA2606A333; Sat, 31 Oct 2026 09:46:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=EX+rzLR3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09CA31F000C1; Sat, 31 Oct 2026 09:46:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793440005; bh=aFAIeNXgFr1JMM5WH77Fc7EqldEyl6IknIX1LhJHwrw=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=EX+rzLR3sPZ/JAPmDxO6qvruP7KweCWYbPS+ljbCCp8ncesIMMjQFWL1CwA/7qSfO MZc2qDD1LCXFUhxjV2Wh1MkDNJkf+rR7cRYaaywcEG/vgDTdJs73AERbIuvmnhE1S6 H+m+yHY/9r3a7AicVf4tzMRkrsrz4IKZTEYKWfu6Qu1s/KRba/wlS2kCTK/e6cNvcp fG7t1VvwaN5GFTBzBdF7Y40XCg3q4K29QXyXbc4wZPl9siKtYXSZ/Kcf6Q58L4QyHS YigSSln0JE5OvhEsT/dbdRmsbNjFGtOnAHU+HIrXMBQCDYGCScxOz39ya44Wul1aWT iCtQ2jWApIcOA== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:54 +0100 Subject: [PATCH v3 25/47] mm/userfaultfd: wake waiters when registration modes are removed X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-25-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> To: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3059; i=david@kernel.org; h=from:subject:message-id; bh=jIZ4aj6oO0T8O1iDgAYwxVUGJ5PVlOxvrE64yrDPOpw=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs+YcELBdt666LezdhU52py4HZm8/dli+Q03o4qWM xRWFxqs6ihlYRDjYJAVU2QJCr5v8PLlutpqNz5mmDmsTCBDGLg4BWAianqMDO/D2137GiO5DPhs zh344W9+yLuP8c+LXNmID1+Yjs5d08LI8PXN7dVm34SkfnwM6C++9qtg/ZrPP8T2TW/qe7h+anf SCx4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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 Signed-off-by: David Hildenbrand (Arm) --- mm/userfaultfd.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index be630674fda9b..03f1b15bfe63e 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2270,6 +2270,9 @@ 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, @@ -2287,6 +2290,8 @@ 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)); @@ -2332,6 +2337,10 @@ 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 (vma_is_hugetlb(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); @@ -3648,6 +3657,17 @@ 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) { -- 2.43.0