From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B9651E2614 for ; Mon, 24 Aug 2026 10:12:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787566353; cv=none; b=I4kjP9+XGiOXw9SW85CXP+pxEbMUcSHBM7fT70c+ufld8ECYWDA2FPm5IZ4d127GYDCEZPO6yKb0+SnnRusaMucruHzCYsLiY1pI4653eTaAWjsaK63+xie7gLUxdZcNdMZtiq7vTgjbMRq4z9ozKYd3DcTQzeayevZdYvtzvyE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787566353; c=relaxed/simple; bh=shpmyYJZExr57zqGCbJbhoiB6Z8GwisMUuaDpKltrhQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jsLC+AiDZWNggONUMisW92OmNdVYOePHJe9M9xy/HSD2GL1OSqdIMIBUknzP9NnTlpkPPeJNIIc5s2o4c2sXUPN1fQzguOSYP+yvKfsOkskM4BT4yQ9ZTglK4EjngUnuPHvEU20Orz2iqy0NuqlECPs0hgFTDwSB6YwgD5YgDG4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WozWsLt+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WozWsLt+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE80D1F000E9; Mon, 24 Aug 2026 10:12:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787566351; bh=WhPzGv/jLYWIV5rqDmfbQ8SCSY37BPj6+XKV+nPgTVw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WozWsLt+jB/GwRyOYpg2/YGtYULCzHHuEJpJhazxcp8ETvCFkDdwRoNSym+MQGejs sw07//fH8xUWLNlxFkxJBqDzZsOv+VCC2oqyFOow2V8rtcYQJKa2W4zk5uWoXRe2wp vf4lN/qY4ylXf6s3RQURtB7g2gceM8spgXjsx7diC+PjElapTxuzpe8ejROVGvwVCq jVuk7WRd/TamkCkgLV08AarxtRCXlQ7pPvAKelcSJWZyn1W5+T3XUBGRlPRxXAj7vc RWD+iWeIXKXjzq+5rHjyQnKXZCkHlwJvaYoyfO1OE3Fv210uvY1zUsJYQrH1aX/jSN rKQjxGzwSEZvg== Message-ID: <19de764c-467d-4472-8c85-a84de87bb702@kernel.org> Date: Mon, 24 Aug 2026 12:12:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mempolicy: Fix sleeping allocation in alloc_pages_bulk_weighted_interleave() To: Eric Dumazet , Andrew Morton Cc: linux-kernel , syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com, Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org References: <20260821170407.3721004-1-edumazet@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/21/26 19:04, Eric Dumazet wrote: > syzbot reported a sleeping function called from invalid context splat > in bucket_table_alloc(). > > When rhashtable_insert_slow() rehashes the table under rcu_read_lock(), > it calls bucket_table_alloc(..., GFP_ATOMIC | __GFP_NOWARN). > If the bucket table allocation uses vmalloc, __vmalloc_node_range_noprof() > invokes vm_area_alloc_pages() -> alloc_pages_bulk_mempolicy_noprof() with > the passed GFP_ATOMIC flags. > > If the current task has an MPOL_WEIGHTED_INTERLEAVE mempolicy, > alloc_pages_bulk_weighted_interleave() is called and currently hardcodes > GFP_KERNEL when allocating the temporary weights array, triggering > a might_alloc() splat in atomic/RCU contexts. > > Pass the gfp flags (masked with GFP_RECLAIM_MASK to strip page-allocator > zone modifiers like __GFP_HIGHMEM) received by > alloc_pages_bulk_weighted_interleave() to kmalloc() instead of > hardcoding GFP_KERNEL. Since the weights buffer is immediately > initialized in full, kmalloc() is sufficient. > > Fixes: fa3bea4e1f82 ("mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted interleaving") > Reported-by: syzbot+0dbf6d295b3350944f0b@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/6a88837e.ae6ddae5.3da009.0040.GAE@google.com/T/#u > Signed-off-by: Eric Dumazet > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David