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=1794591198; b=slHKhRy1HxMH5n9d4WcOX6dbEXUuRzHKqPggfC19n7FNdxnxUZzuSxVHS77ZpvQItuqM bxE+Q7oHHIyjPrbRp9aabpA6GSZXBOnplGFWyc4JRBJwr61SNawVz8Ur6AHVoa3Je2Q20 TTzkWTn7FafrEpB8+3eXHhtl5jOiCMeJm6n/8OJppQX8XBn+L90y7KvDHqx/16Kqd7ZRf KMJP0HDat7m5vrflddFcALWRVcT9QQnWrK68PHrQdidx36G7uhykhG3ZVoFfh1NDOMLSb wGlbNpAoX4H/2dV5Fb5peyBOTg2Mk0YP1Tei9Nfsa6BGRlQuL2zgYgHUhXoh29hshBQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794591198; 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=t737D1/nAMghJEj0vM2fiTLWPiB/m3r2uY7xrIauqsQ=; b=qT8qfPzHyBx76/lhl5Z8ibKlq5Mu7zgoIekrFG0MDje8FZwz9Ip/dA7rNlFgDKheMTxp +RNrIbvIDVxso6hbOSGx0l6Ky4513dihYJOxQrpL6LRXNFZncFNgx3Mr/A5QtO2YcBd0H f3qPu8hbREltDgzcNciMAS3xqGgc8G+6JgmUINz1RxToT84HALPWwTxi5N5+y6KIO1OSg YVrDTjOgSrPiLBvQhL25Ba9rU2bHQDhPerUZtS2/S4nsNMb3DhaMnbBUWAsIwQyLWdB9X 6tcqa6x33fjOFt3sZDY/++nF0daLMBWOtErFOk1kZFku+R28I6Zsj8qs/IrpOdpzO0A== 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=2m3bMvQx; 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 CD09E6075844; Fri, 13 Nov 2026 17:33:18 +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=2m3bMvQx Received: by smtp.kernel.org (Postfix) with ESMTPSA id 786A61F000C5; Fri, 13 Nov 2026 17:33:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794591198; bh=t737D1/nAMghJEj0vM2fiTLWPiB/m3r2uY7xrIauqsQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2m3bMvQxkJ7snpN/cva6Xx5JZx6lwdbcCw8hylfTEF67iIvGnHeHl/7fXnLLa3VHT IvSU4Qag8c2cu9vuJDL4Pa0VHKY+TMj51FL8OJuVWV0kw1m/1RV+NhLA+p9JImpokC hX1RBZUWCNkoK8H7kz8G1VmVvReiObX1AP7aQ1iU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , "Lorenzo Stoakes (ARM)" , Muhammad Usama Anjum , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 6.12 332/670] mm: fix unkillable fault loop on MAP_DROPPABLE memory Date: Fri, 13 Nov 2026 10:48:16 -0500 Message-ID: <20261113153823.120621510@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason [ Upstream commit 9f02ca8c15a74bc9e4e8e05ec089f63cb87cbf75 ] handle_mm_fault() suppresses VM_FAULT_OOM for VM_DROPPABLE mappings. For user-mode faults, pending signals are processed before retrying the access. Kernel-mode faults on user buffers instead return directly to the faulting instruction. With persistent allocation failures (esp. memcg limits), a syscall, such as write(), can therefore loop while not dropping locks. Only suppress VM_FAULT_OOM when FAULT_FLAG_USER is set, allowing kernel-mode faults and GUP to fail and signal allocation errors. Fix generated by an LLM and sent by Chris Mason in private. Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Reviewed-by: Lorenzo Stoakes (ARM) [ david: simplify description ] Tested-by: Muhammad Usama Anjum Link: https://patch.msgid.link/20261031-fixes_core-v3-37-d6437171ecc3@kernel.org Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/memory.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 223f82aeeca5e..564c0ce0aa6d7 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6121,8 +6121,12 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, lru_gen_exit_fault(); - /* If the mapping is droppable, then errors due to OOM aren't fatal. */ - if (is_droppable) + /* + * If the mapping is droppable, then errors due to OOM aren't fatal: the + * task returns to user mode, handles its signals and tries again. A + * fault from kernel mode has no such return, so it must see the error. + */ + if (is_droppable && (flags & FAULT_FLAG_USER)) ret &= ~VM_FAULT_OOM; if (flags & FAULT_FLAG_USER) { -- 2.53.0