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=1794438303; b=sOWtVBNyxdd733psqNIgDG+D3ACzfuwDSY6XS7roEXRv2ygNgu2YnJVFgcwrMdtOK00m aM/ZblUAdIaaeEFzjSAYaZhxR8DDG+H36CFljdgIlHegKNQyCP1wcJcaZvdQU3AJTXHA4 +GFGKWaEhgPMk9TQlSufRFP9LdjoA9533dPRKUxkMWWGa/WBwQ5RrYUl/Oe0sUIO7dcrV O0UsHP7Ay2zJakecd75CwJtWw2Ym7swD3QMuSBhNdZhC6IzvqDJn8WGmT7Sd0l8yrs72M qZ/HfBQJwHMjBV3IIaC4IOy1HzFI0l5YsGzTFksQHdxuFylBqUvGfB4Sn/7nIxQD4Vw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794438303; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=SP4kKZr1/rxDpDSqBCS8ofh6a0EM3fbwBhr6xrSIS7Q=; b=gGTY6kAvRXmYU/d0WRnsFgIbCx0VpHsPKSWpmQTbi5q9KdIRtKaXPaRnRDkVyzLgdFuv 04cnATfyghTnSCuVAytzFvvqZ4Q5prjzaeNejip8afr9OgnlUF748O1p9IUHTj6C3qqKz c8YQAi3LzW9qfB/ymzoHF11EDhhXuZ9GxxCKRDjfKe7o5hWx6jPO8asOwdNp3EewGGlZb f9GPX60+Wdh1v/KlDM3RlikSqRHpYxg6iBbOfkvgMihVKezZit2gmDN7s1hHGWhC84/Br ztM9TSHihHxZEMaHxy5e3uoipAmpf/tsWd8sf1c79SHD2GMrx1tySq+jAyKxb/5bB3g== 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=gGW3WEcB; 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 AC198606A31C for ; Wed, 11 Nov 2026 23:05:03 +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=gGW3WEcB Received: by smtp.kernel.org (Postfix) with ESMTPSA id 815B71F00A05; Wed, 11 Nov 2026 23:05:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794438303; bh=SP4kKZr1/rxDpDSqBCS8ofh6a0EM3fbwBhr6xrSIS7Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gGW3WEcBZzwhPxkqlF2+unEElVQcARfz+A/YckpRkrDpN+WmN4UGmU7TX+KXGG7/s g6coDJIRqaZu29d96sZXS7A22Z1lposOI9b2H0ftQkva7nintzjJeiyE8tNse3GnhO y2D3G9u+7W8qd8AdeiTbDzdskYDSc97jLJSySEeJgiMblePpt1vSZfrd8XspcY/rHp 4c6aY0alXawf4U+bo6ENASGKUpE7sL3CoKRYGtnds1VlG8yeC7Bj7NV7opOj6y4VDC mEbdmwKZyWu4sAJk7vsdC2LkHi9yZU3hKf1LtkH6lxsG7RX1V/JPwzhQy+gQkSzhvU BUd1+0aoUsmyQ== 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 6.18.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 18:05:01 -0500 Message-ID: <20261111230446.377585-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109200508-failed-6.18-4eee9c389b07@kernel.org> References: <20261109200508-failed-6.18-4eee9c389b07@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: replaced the upstream wakeup wrapper with a direct cross-file wake_userfault() call using a shared range structure ] Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 9 ++------- include/linux/userfaultfd_k.h | 8 ++++++++ mm/userfaultfd.c | 12 ++++++++++++ 3 files changed, 22 insertions(+), 7 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 7e40eb9131bd7..22d4a7ad54575 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -71,11 +71,6 @@ struct userfaultfd_wait_queue { bool waken; }; -struct userfaultfd_wake_range { - unsigned long start; - unsigned long len; -}; - /* internal indication that UFFD_API ioctl was successfully executed */ #define UFFD_FEATURE_INITIALIZED (1u << 31) @@ -1191,8 +1186,8 @@ static void __wake_userfault(struct userfaultfd_ctx *ctx, spin_unlock_irq(&ctx->fault_pending_wqh.lock); } -static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, - struct userfaultfd_wake_range *range) +void wake_userfault(struct userfaultfd_ctx *ctx, + struct userfaultfd_wake_range *range) { unsigned seq; bool need_wakeup; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 796a380664bd8..d65effb5cbff2 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -78,6 +78,14 @@ struct userfaultfd_ctx { struct mm_struct *mm; }; +struct userfaultfd_wake_range { + unsigned long start; + unsigned long len; +}; + +void wake_userfault(struct userfaultfd_ctx *ctx, + struct userfaultfd_wake_range *range); + extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason); /* A combined operation mode + behavior flags. */ diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 579445bddf561..5846fbf8baa09 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -2064,6 +2064,8 @@ 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)); @@ -2098,6 +2100,16 @@ 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) { + struct userfaultfd_wake_range range = { + .start = start, + .len = vma_end - start, + }; + + wake_userfault(ctx, &range); + } + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); -- 2.53.0