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=1794585706; b=rqRo01aNo4EVEnKJgrP87KiX+id6KVilWlBswdFrLeqTdqEfFkqIs8QHJgNrBuQ1vHJv aIcwiGSvatbao0HeUtNX8+dFchWxdnBFAmZQ2IPw6GhiS9J1fF92pcecZ9DHZvoyFaosS KOHLONHcQvgTNhIG41nLx7flS5+VdLVrXVDE8IxfdVUVGNdXBjhuzSoIXzA02BZnobhCD YHoWzP1Z+Az8iJUyYFqDlvAINOfAYSNrtiqlehj1JOc8urDE033P+XSq4QSZg44pfWxLM y7tVtlN/SMCSRKDxxnV88TU3rUtB6dwEXEARp7INK6Unlq1LS+uMM8u0+3/LZp2mEtw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794585706; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=V/6lFsfkNS4u5/l4GEz0/y/pHVK8P8ygi6P8VYS+opo=; b=c6FMGsAEk/YMzNs0Swjd0c2IgQ+aenyFpIsgdWnHWrnw+GGjn/ZaiQlFXYSh94tVB7Il +R4Rc3yQyFOlmOZXNkf0fUtg6jyEyqvGbJc9guurnZOduA2XjzhpJflY4nDwXF2yW5Tuv 3Kg/tMmjW5EfSfsEgZyWFxONBATmMqWY5npasgONyU/YwdnUuIAtharOXwAMezj/CVXso GMzJ+lOwBxFcvr2mKTBLhcK0Gs8O1HGUXOOjwQIKDTHnUU9z2lo+RrdLOHqRADJBTWcCd QndR83nyiinSzf+4prLI1mJcgfJWnskU1jIlthby+2MMX3ojw8AUh18ovccf2iQtKeQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b="K/kCaoFj"; 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 C331760A3839; Fri, 13 Nov 2026 16:01:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=K/kCaoFj Received: by smtp.kernel.org (Postfix) with ESMTPSA id 728571F000C5; Fri, 13 Nov 2026 16:01:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794585706; bh=V/6lFsfkNS4u5/l4GEz0/y/pHVK8P8ygi6P8VYS+opo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=K/kCaoFj4SEKkPt7CoZDSz4kY0FUFkcHu9QflJUwmmDYqMwVndQ3d02LrAX7Y3Jnk x7mrF/tlhWyoWAIwhNzjsx+99GEiAGTpcSODB7bIdf9uUPBXN13jtnMh7gyGIvD+GA kHLsGBHEBKSAp27YHuVIBDPxNaZFCdar8IHrIIzU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , "Mike Rapoport (Microsoft)" , "Lorenzo Stoakes (ARM)" , Suren Baghdasaryan , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 7.3 311/507] mm/userfaultfd: write-lock the VMA before waking waiters when unregistering Date: Fri, 13 Nov 2026 10:50:15 -0500 Message-ID: <20261113153805.914996786@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153753.358973689@linuxfoundation.org> References: <20261113153753.358973689@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand (Arm) [ Upstream commit 35f7ecd55ce7e51cb6d5ef49e6dd51f3c80f61e4 ] userfaultfd_unregister() wakes pending missing faults before clearing the VMA's userfaultfd registration. With per-VMA fault locking, holding mmap_lock for write does not prevent another fault from queuing after the wakeup but before userfaultfd_clear_vma() write-locks the VMA. That waiter can then remain asleep indefinitely. Call vma_start_write() before waking waiters. Existing fault handlers queue themselves before dropping the VMA read lock, and new readers are excluded until mmap_write_unlock(). Fixes: 29a22b9e08d7 ("mm: handle userfaults under VMA lock") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Suren Baghdasaryan Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-23-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/userfaultfd.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 500962be11624..ddce409db0ad7 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -4035,6 +4035,9 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, start = vma->vm_start; vma_end = min(end, vma->vm_end); + /* Prevent new userfaults from being queued after the wakeup. */ + vma_start_write(vma); + if (userfaultfd_missing(vma)) { /* * Wake any concurrent pending userfault while -- 2.53.0