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=1794439687; b=iX1PsnB81QwMILCB+E2q6s/vqdGGmdTlaLnZ1CBHXix7RR1Zt2dBpErdRCRemFXA6rWn 5OM6MclB7HKaGBIgL9nVYb6iTGGFdMVDPEHBwNmR8NQC0JTIDrUiUPwKdgSj0P4MCOxVz eHN3nkXZvcBqHR9COSWmyEacKSk0J/hMqkBmjbbnBVQYTmqk3yxK1ndxuCT/ldJRi0ASA aevf/LBRzYZOEwjJ86nPEVrGmW8fKz8AE53J8gM5XZCcxzKoCec5CLR5O0KBAAy8DssJW 49oa0aHMcc2Cmey0OBXgAFrF75cT4ifhTWta+8BAlrLOaNGpjhKcJPIyLq/df+2ShWA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794439687; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=ibh16hckzSf0pI3E7zle1ONFLmqUDn4zHjbVKC9sGMA=; b=RWDp8jWb06kR1k/yx1mgSElw+ye1awCBGUIIMilXFf/HPpBkkc2krSgy2KL2zERNI/aG varwmVh1TwhjQOgCzrxFKlG9RvwCchkhLu5Hs4cGWDy7bCUaMyqb+EcilV6KgvNvs9+G2 n6yHTKP5mGGXS06gSp7jGTDDFgv6Ljn6RwP8trQGoXYT3KfwYo/KxMPY6CEOCTr8DSH6p vqs3b22VdlgaxgmAjAikGd2E2QrjcW6CKaMBBtJ2ovUvCQT+QpbsNuZMjVOHmV01zAlhY rF/EM3OxzanZn41f+/xEWne3i+kUYqciJVvIF/2IhQ4uYi0t0BIvaFLnS30uN8MMWRA== 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=JjSXpp7H; 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 CB977606A32A for ; Wed, 11 Nov 2026 23:28:07 +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=JjSXpp7H Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF1F31F00A05; Wed, 11 Nov 2026 23:28:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794439687; bh=ibh16hckzSf0pI3E7zle1ONFLmqUDn4zHjbVKC9sGMA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JjSXpp7Hcvjdv8i+uqmpXHyQ5xMLlMJBDpoeOyv/N2Gsr7zwi2FpJieq+Bh6F2dhx 5pmqqjrb7Us7uoxgY72D3Y5c/WMZXT0u+i8gre6kvL68moXSjyfS7BkNkAn1O8jGj5 X42iZR+DGDjqfl0SvfSE4sHEkpKK4JF7DcRH1ymiJtXGJbC0G+2w6tJ3LmQR3fH1X0 Sz/hSwVPO2tg75HC1ZeAgnbj7YYX+uUCNYb8tbSwOVCGK7KrhN33DG6KOgMa31xvE9 /8JVZF5g2ta444olocHk37Yqet+kIdP7LBaYZBViPWggThTKm8NmJvwnX+cckYHa3l cmwEE2UGdIC4Q== 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 6.6.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 18:28:05 -0500 Message-ID: <20261111232739.585501-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109201339-failed-6.6-4eee9c389b07@kernel.org> References: <20261109201339-failed-6.6-4eee9c389b07@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: adapted userfaultfd_register_range() changes to the existing userfaultfd_register() loop by inlining the wake_userfault_range() 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 bd64d6b9cf899..273b16516a5d5 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1476,6 +1476,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ret = 0; for_each_vma_range(vmi, vma, end) { + const bool any_mode_removed = vma->vm_flags & __VM_UFFD_FLAGS & ~vm_flags; + cond_resched(); BUG_ON(!vma_can_userfault(vma, vm_flags)); @@ -1527,6 +1529,16 @@ 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