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=1794585729; b=3ixASIAmX4acchn6GYFgXJzT3TuoBn9bCMCWaqVVNXzJepCiWMogAJcegpbMEVOp4/YM 0U9ZurM7uNmWdsQ4yt94zkDPB6FHRw6mtX6ghnf+x3e3UGKVyGVUktKBGb0qvBJeAVKMQ DK91iAybAvfz4S1zoaj4iPUMA1UldzfoEcaBIAlDHUPRXdSFZNEDe2Pb+jXcpnWVrpq0W FziCJoMweavqEaKsf8TLFVChnl26Y5VQamG1wuvuaazYfs91MOb4y2qy5u2koMudDjMmD X7d7Lvs369EKT0amcNmeEhY23t1OydiVxPWQNkGemtplBLy9WrPr5dx18dUmjTK1YzA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794585729; 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=XEoQJecVa4KKtRPbUxSPnwgBeWOXcSXl+r3TBpdMpjI=; b=R0u6elGtlHGa6WojVMooC7G7IesOGGFpTPtzgS/9Wa85JFZyv0ulCStMF+SP8oOu0SA9 b/G7mQZXRHqwJB2MQR6PHpPA+bqDA1lvoYzgtgAsURtnDrPSy1lzC3a7YVcwwf5abK0bb YXvTYU7q7UmA7BWdmXCg5BhH8P+j+O/WV2cvW1Av8X/7jwbd2zUewaW1M/wy8GcnnPkl0 /Tiu9NDyDDck/+0ZAS4zZYRtCg/mLxwdzB/VnJ1uW6GF0B0U29nTO4gciVLJMCZMuSC9G qNqkRxIQmtxyOeWS1LD1myNwBLk91Yrh56aj/dztqQGbO2AAXXxUbq5/0rbq5fbdgMA== 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=Me3V3WyE; 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 00699606EB88; Fri, 13 Nov 2026 16:02:09 +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=Me3V3WyE Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FD961F000C6; Fri, 13 Nov 2026 16:02:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794585728; bh=XEoQJecVa4KKtRPbUxSPnwgBeWOXcSXl+r3TBpdMpjI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Me3V3WyEpULL0vKZoAILv7Iq+z6WFrN0Q7tlWwSDH1Q+sH2K8K2WWd5vSHnyVtZ/O NU6F1qtIiV9qgOX/EJDs17s2vqQ5IRK0vk5dSxVpF4hORZfVyM+DmkRKbs2Af6tpVX 86cOe8UxTz3tSkkw4jRxvaGHgVj2qQeVX80S7V9w= 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 7.3 322/507] mm: fix unkillable fault loop on MAP_DROPPABLE memory Date: Fri, 13 Nov 2026 10:50:26 -0500 Message-ID: <20261113153806.308224767@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153753.358973689@linuxfoundation.org> References: <20261113153753.358973689@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 7.3-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 e773d51f0d6fc..f6f704d693f4f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6923,8 +6923,12 @@ 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