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=1794440680; b=5K1x87e1KHKmgDk5XZJO/m36ZsE3WopEezV8ovZI+gIiBJIqZ5G35Wvn5g5J7AHF1xNb JLy4DBc4OHlmsoVKYFQmR954BhVcBaxOxFyYj/FUA+rKcAJ6z0kPildZfiXJssirXa7V+ X2RiaDjMLlpFMsE4vqDuMwBKi3Qc2xdrICZxXVeL+T9BX6h0Zavb0X/9ddwjfQx9q8XGf k9AcGn+YbSmUOZb1mJ8z9kDDvDQ7Kh2XU4qRcEvlmdtnJFZM8irL3TP4uPQktSGwzyIco NNjlCFvOIDSoGGkAM4ZIDUcgoSbKMovlB8sSYw+WjF98nJsAGv+vxtoKz3l/gp2YAHA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794440680; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=hRtRWsNDT0E4ihZ7rKloseKdM5fQEm23ENBT65T6JSs=; b=h/kzzoAqurJt7IbQDktLVWXyJw+2K0ius5U7mtX+3fo9f/R4iA1+z/UjJZioLuNLlt8s e+cUxe0VzVRbCp9Q2LixiCCNXxmeulWoxVNcXJ1a/Ym8mqGjxox76TWaTl0McjT4JiqhE IwooIfI+MAWfwR4QpOUQZ3lapRg/TF2akxC2/JAuVx6zEVoCu/AVNtlbb20vQWobEL+bI cgCYZNVIZKkdjQXiXo/m+SldlQ5vTRZG2575W/QAKL+Q90f2sWuCCjsf99nUey/0oIvsg O17DqtgN77b32HkHTPn9omLl7tYjJjdkpqGf3tqEdmoBJv3T/UuLYm8JD125MYIaMOA== 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=VOUCFFZH; 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 4C110606A31C for ; Wed, 11 Nov 2026 23:44:40 +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=VOUCFFZH Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D2291F00A05; Wed, 11 Nov 2026 23:44:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794440680; bh=hRtRWsNDT0E4ihZ7rKloseKdM5fQEm23ENBT65T6JSs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=VOUCFFZHcPiX/ANMXF/QKOXDbvzB06BrGL6kaDgFOmuiE7XqlJNPRJDIHOX4t/wE6 hD4nS1ZY4N2aTjWtzFjj84+HywL0P24HmCs6CTaDuydr+zF34c2u11AwmRjE2DqEi9 x9y0Y/OFrFyIUVzYlyi9OmxHPDnZwOA6iiPJ8u/Z0KWYbW6qwdO0pIiAT0SKUqpyQZ VIt/Hps/p/DXrIJ6s3uE3Jyf89QuHeZEnLrfIoCc3R/pjJ+k1lm5oDNOCSx9nJRO43 fPVMjMDzdY+jWA3Jl6wDjq+t5ir+00lWApO1IwUuzoJ4X2YQCZoVCABR+b79zionWd 15rrOuo13BRFg== 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 6.1.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 18:44:38 -0500 Message-ID: <20261111234407.676040-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109201823-failed-6.1-4eee9c389b07@kernel.org> References: <20261109201823-failed-6.1-4eee9c389b07@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: inlined wake_userfault_range() into userfaultfd_register() using the existing wake_userfault() helper ] Signed-off-by: Sasha Levin --- fs/userfaultfd.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 59c4fd41a35aa..7a23fa700ffd1 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1450,6 +1450,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ret = 0; do { + const bool any_mode_removed = vma->vm_flags & __VM_UFFD_FLAGS & ~vm_flags; + cond_resched(); BUG_ON(!vma_can_userfault(vma, vm_flags)); @@ -1504,6 +1506,16 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, userfaultfd_set_vm_flags(vma, 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); + } + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); -- 2.53.0