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=1793057141; b=HqIVp2F+EZWH70D1vKSKbFklLOIsTuytnz/CSTlSW+V1J8W2/qxQciClKy3T0H/2lrWx KhQGGTOXK5MmVBVabLkKxdrNz1WooTWcxejYR0qd/2ZpWfZdW2Ll2HDYI5LkYSXtyOicn wJuOC4kn+PR01mEoavu+UsGCXY2vGTjIUnpj7ZZn8VSLmm/wqYy6O9nM08229bLHa6AcY cS1qEKcYtiqCvTjxu7A2Ygio9AnlvZPNXRTM2v9XEzgsYcDCnEGmv4ZdP3qIoccqgfXnm 7V26XnIEwlmHoSta47NlAsioXfoY7/HQSRYycVW0mj56osSwd8MzU1K2Kxq3H4c+tNA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793057141; 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=d4MV77Ak5yM3C1+7NxJwT8IeWvwmREROuL+a3NtDfRQ=; b=QHUHpheVnFzTM5x+q7oAG4bdG8d72vcgHeUCyDFJJ7OxqHbgW1qB8Zu6khdWkepgyK9L /WGzAfEpkk9Ihp0jBV4e9it5Hw64blzX1VR+R62OlLhm+BXhtLxO4YMpGcYV4nLnczQ5+ fa0KLKOB1s0Ml6eRW2ug8wnwBsoNMGde0oLK4P25K4/QlRd3YE+W2oRhdo9pBWe2bda3+ I3xw785Bb5YUKp2qahNyFmgpWCdO+xlc0Firs6bArATK6vJu8uAbp335BUZ83rMExN8b/ vxniBiiEDeg5rYGA1oAGTvRWjowX95U8hAhsda/eL57B8uu7y+lCiAKR3tofuOB+J/g== 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=csHXg4wZ; 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 91014606A31A; Mon, 26 Oct 2026 23:25:41 +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=csHXg4wZ Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD50C1F01825; Mon, 26 Oct 2026 23:25:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057141; bh=d4MV77Ak5yM3C1+7NxJwT8IeWvwmREROuL+a3NtDfRQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=csHXg4wZ8V2CmRF41ciyNKcq+nBGY98nOFGquFQV1I4FOR2ZqNkkrBhldXkbQA73s kqedJrXPlEw/GuLeiEQWDKrNumdYNi7vhd3rTRVxjzw/ieirH3dPmp6u/as6YmvrVJ iZVtw5PMFX/jnw2wY7gllsWdINeETnRlf6f6Vsm9gTVUB/vzHDYRNW77UUNKHK5vf0 Bqeq21Tg4d6xJhLwKyTxEuaoXxDsLIbY0SrDQTLoSeu3UpGhMLhfsPmkHFvrYS/6oI c2/1w6D8Hg0KPF7JckRXaIQGKRF2A3XeW1iG0jHdwzqpLBslT2ot9ceobK3MBvzzoe qXYq7+4TRovEQ== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:45 +0100 Subject: [PATCH 25/46] mm/userfaultfd: wake waiters when registration modes are removed X-Mailing-List: linux-kernel@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: <20261027-fixes_core-v1-25-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@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, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2728; i=david@kernel.org; h=from:subject:message-id; bh=E+83r7S624k5EPCZEmcEXyyfHzl5/kgAEPI++IJBHPI=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35+WIeW5rKpx0pvbIdt016lonXeLtHmhY9T1TzZjs 2/d3hvsHaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEzkkyUjQ1votYCOD5eP6p1d wta/KW2Lx6N81v1HnfwbZF37HwhPCGD4p3Rb9PXpo3MvSN91cbu8pm+zTknZg8xeGZ60n/eON9n vZAIA 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 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 2122676c4220f..710e913c73bfa 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