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=1794441091; b=zCAvnkUbLxQu+EsOZPXEkbWb6+rsFr+zlXbA6hoJebbiiL88Ge8JTIUeHyevUqCRxBQF EMYv6wYxoZlzTjzOt3BYli/hkq6WIM02Ch59khvqj++2fdJzSlJzmntDHLnzsdGO2kp8U WhVccb4Y6248O9JKG5GQwaZNN0vAG/IwRJ9vk+BrXW5mFx7WQ1DaUTDcDoqjjs7OjAf7b xH+nFiAJcj/7saphCw90iIHYUOKA0N1YydZJO4Q4JyQhpx4stz7sUGiJ5Xj4butN1y8eQ XJF0vNfJ+wui+lOpIcFHD17263NW3sIr2rvOgovMW+I3nKITcHoxI3xckqYaWR+WfVQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794441091; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=UdR8M71iloDlSCOFLWzcAf+uOGgX1xcxn/kg2mNFgVE=; b=EfY4Nxdn7pMH1pbARoYwXZlL2J2NiF/v8jcPVVpG62XbY9XWkwn5ZfW4/zSzGoZsC3nK p/536Nf96kAehi3h/ryA79FQ/p53cZsajMkdc3q/WafCH+RW+duvH2TSyzHNOZDK05/lW AfJgoW0r2fvMEqhWynaE2zd2zM2LVD3+n6Pa9dVpQq30+0jYyry6rXYDmW9ip0/1DH4A9 Zf+vbnuxJxspXbxN992k/HNbbcRwJJzPfIjvPRKhYjoJNwFpX8Q5Nu4fIIXCYd6i6u3mo w6DeyvbH3n883kzZVDdiuHsMIuEaGhj/9BYXQLYjn0YD4C6WPvJiqd6ok2jdBaDc66g== 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=USzXQD+o; 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 32E78606A331 for ; Wed, 11 Nov 2026 23:51:30 +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=USzXQD+o Received: by smtp.kernel.org (Postfix) with ESMTPSA id 00D961F00A05; Wed, 11 Nov 2026 23:51:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794441090; bh=UdR8M71iloDlSCOFLWzcAf+uOGgX1xcxn/kg2mNFgVE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=USzXQD+o6bnRaoyn3cNVLXRt5Upj5mKzhLaSpSoCso43ih/XKcXRoo73YdsN3uQn2 NE99kH0qTF3Zttj+WZftCVFnvuaJ1nqEf5WC97UxjY6AiXUo+OXtm4n0J+wIGEYm1B 3GMjIEIQL74z0EMzOrE8LHhyoiAviqSMkuSG4Bu2s8WklGWesd8LVC5eBsEjFFDptp Ab/RfejVUB0tTUeRSLovXfABttElt/i0vBY4Os/qFinrM25CN/7jDYcRH1/eNDDS0W 3saNDDcgeHNeISJA2q+d4y56kKwAxb2SMqkPFHM+jsQGmtJFiS+r5mlXpE53tMJ/Y1 VU0HiLr3d3y5A== 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 5.15.y] mm/userfaultfd: wake waiters when registration modes are removed Date: Wed, 11 Nov 2026 18:51:28 -0500 Message-ID: <20261111235106.828557-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109202331-failed-5.15-4eee9c389b07@kernel.org> References: <20261109202331-failed-5.15-4eee9c389b07@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 wake_userfault_range() with a direct wake_userfault() call using a local userfaultfd_wake_range ] 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 271ce399f6b6f..ea7e9db135eb4 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1421,6 +1421,8 @@ 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)); @@ -1468,6 +1470,16 @@ 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); + } + if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) hugetlb_unshare_all_pmds(vma); -- 2.53.0