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=1794444644; b=oaGyGOA1UqHeWEgajMxC2nzvLNKSwTU93XHZFVt8fR2JzH78AnPDC/uqX+JB4OHRbqgp 2y2YMyzHI8LRW6MWk9nSyyssjpUYmagYtvkZZ28norJ7lcrVFWAVMhSb7MNRYG69ZHYdZ dsmMGnSvOz7FpdSzcIPRc4EpVMlVblHGZYCrUk0vr5uNWwkzVs7/+4LphcWVPDQSM+0zv E7hSb9umAzjc4N+tsHSnYSCiT6QXHA9UO79odPyozAkGJj2vbVlMwwwL0B3GQvO8iuchI /tdex08fMVmxFLDZd7KGiFIl+tLC9peil5+p7zaLNNAEzZLQ9DCrXkG9fFFv1i1m/vw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794444644; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=CKCgvKC1EVo3K5cTJfvbp6FtPhrlED0a4M7wVowEPAM=; b=xkAX7Kgzn0Kz7RNxT3lThjXpJhZBktLKpLV7YOZ0wBi03Hy9ELTaojqPkVFE+KpNyUip 7PtaQvXJ1Tn78JQnRkU0kZW4wFB9j6Vp+UvjJYFQPsrCSOUNEHaU3/TlaT1ZWfWPRECT0 1JA17OJ4FzFQcs7mE2Lt2m/cspmGGxtsS42zQNOdjao5XFtUWU5i14Quh69vaLj1WWUIO m2Pm18t09uFjz5cWpjkNBStgxkBFqMmJdnaF/3xbH7gIuM07fWXGdFnLjxdmy2NORrNZx P5BTdnMXbk8V4rBsmgTXQJtFphJgdaRiKom/KqIAnV1TXJUQ9wGwHH4dQOObapSwy9g== 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=Q9fGA8Uc; 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 392BD606A326 for ; Thu, 12 Nov 2026 00:50:44 +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=Q9fGA8Uc Received: by smtp.kernel.org (Postfix) with ESMTPSA id 560D51F00A05; Thu, 12 Nov 2026 00:50:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794444644; bh=CKCgvKC1EVo3K5cTJfvbp6FtPhrlED0a4M7wVowEPAM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Q9fGA8UcNSjcJX0WfeEV+QRooFnIBzOdU8xbOXsI4psiTcql69GmQwIn28+dsCP6c VY39+J6s2G7NlM3jPplq07shs9gTgmDF4H2NRB9D/P35LzEknezqMcS1ZFxCgNSq3X 3PEviQZ5cddGFjI8DJ9Swu0fn/xBqtPbluWanjX/2loIDsEtVY3v4L+3YTlxQzO01c N4zyXWouyUFEkqDs//nY0r1N2ZmXr1Brah+89sPpPufBTnGtMKVs3hLmp3S4f3YD6y aGlSD+q+7sL06OWnc7TjdaLBPiujKMATu6GusvMZPi32JoWAm3DDZzsFfTipWf82mK 7BecXeT1BWQ5Q== 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 5.10.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 19:50:42 -0500 Message-ID: <20261112005020.916583-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109202806-failed-5.10-4eee9c389b07@kernel.org> References: <20261109202806-failed-5.10-4eee9c389b07@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 unavailable __VM_UFFD_FLAGS with VM_UFFD_MISSING | VM_UFFD_WP ] Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 6773227fbe889..21c32d941f4a9 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1394,6 +1394,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ret = 0; do { + const bool any_mode_removed = vma->vm_flags & + (VM_UFFD_MISSING | VM_UFFD_WP) & ~vm_flags; + cond_resched(); BUG_ON(!vma_can_userfault(vma, vm_flags)); @@ -1442,6 +1445,16 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, vma->vm_flags = new_flags; vma->vm_userfaultfd_ctx.ctx = ctx; + /* 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); + } + skip: prev = vma; start = vma->vm_end; -- 2.53.0