From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=180.181.231.80 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793868728; b=sxSMb9Qsv8CLb1LtpSh5GyEd23OT5H2/lrHbkNXV8I2sUMNDkF8wvO8lZu+kNF6XFnoW y77U8LBvjZpUv4RuKRnGCKZ3/bxcUzNO+SkVuP3VQyQ7+9gbq6fYK8w2EjeDoYEMUDbhG ef394Sv1xrs30iloC2ojAtczf0s/0a83XsCPLVnIE5WsWXymnVOqUQp87525qw6GpNaBL HIPNpSR9f+rZZYONXkmM1k3kNBBWGWyye1PpcwXH++tCw0CiWnoxC7z6qWqaKngXxwDdJ zIumAuRxJz/Gk8e78uOzOawV7AfYGGGkQqLaD2rVuYoK0Wgnj7rZKP9jYrMV3khMovg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793868728; h=DMARC-Filter:DKIM-Signature:Received:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=Y4soA1wbGGkJusNMsltnTjlcCbzxXwWGOb9aK3q0azE=; b=MUFCKj4N3OFcis85yHv/HeG5uNj/hZPPr44rjE6vu6TOGJ0xPSVcctqfvA8c2VwqLq2t su3UZIvHxQMGBguSvvBRt0wE/ym16yoZrMNGJ1XaZdd0xJHL89/1DuRXqW0jQM+rC5Omg O3ErqgQRw7eNV9/6FMfHZ/OqS8GA+daV5BTDnMAupiu7gI2oseFfQiEzxCMORG/f3knCa pRaiz0Vq/4iUxFtzPBDdlPNwxbwLTDUEL59MQCKwX+NidJ1qCj88t9N+cIzCdRuZFKRq9 SwZI0sVBGmB/xdfiKO0kkvgjHG1Z5gqlJY52P+Qu26xv7z+TO46496UkycGt58mRSTA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gondor.apana.org.au; spf=pass smtp.mailfrom=gondor.apana.org.au; dkim=pass header.d=gondor.apana.org.au header.i=@gondor.apana.org.au header.a=rsa-sha256 header.s=h01 header.b=hQiyX4SZ; arc=none smtp.remote-ip=180.181.231.80 Received: from abb.hmeau.com (abb.hmeau.com [180.181.231.80]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5AC2D606A31B; Thu, 5 Nov 2026 08:52:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5AC2D606A31B Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gondor.apana.org.au Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gondor.apana.org.au Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gondor.apana.org.au header.i=@gondor.apana.org.au header.a=rsa-sha256 header.s=h01 header.b=hQiyX4SZ DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gondor.apana.org.au; s=h01; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:cc:to:subject:message-id:date: from:content-type:reply-to; bh=Y4soA1wbGGkJusNMsltnTjlcCbzxXwWGOb9aK3q0azE=; b=hQiyX4SZA2tS4OXtKu5IuvLWAXyaLoxbQnJcqusLNlkaedE6ATQ+A26fMjA+DYRDUg87uGUyiou lRoULOF943cIw6tI3K5Gc22hTeG/Ng9v6UlF2mFw11tbJk30wbOJrfqNpzIDiRCPr/CITaVGpo2mu poZo3XOSqfuhiG1btoJU0qjEBRk56rx7Asf3gHcsABOhPh1m1gKk3R9k5NGYbHUEvCMMHcL69Q2+B W3GWTdl/jvFmVLDSrI0uBXfF6h1TC0alZsj+uGooCwXHrg5dbLH2huVft4OF2ZZd/GOlnzvExmkns T6iqHL02WTG56M/nMw7sLkSlzw6ZKMYHcyoQ==; Received: from loth.rohan.me.apana.org.au ([192.168.167.2]) by formenos.hmeau.com with smtp (Exim 4.98.2 #2 (Debian)) id 1xOtC7-0000000BJbr-3JtE; Thu, 05 Nov 2026 16:51:40 +0800 Received: by loth.rohan.me.apana.org.au (sSMTP sendmail emulation); Thu, 05 Nov 2026 16:51:39 +0800 Date: Thu, 5 Nov 2026 16:51:39 +0800 From: Herbert Xu To: Uladzislau Rezki Cc: Linus Torvalds , "Liam R. Howlett (Google)" , Davidlohr Bueso , Michal Hocko , Baoquan He , Alexander Potapenko , Andrey Ryabinin , Marco Elver , Michal Hocko , Linux Crypto Mailing List , Andrew Morton , Thomas Graf , linux-mm@kvack.org, linux-kernel@vger.kernel.org, maple-tree@lists.infradead.org, Lorenzo Stoakes , Chris Mason , Alice Ryhl , Andrew Ballance , stable@vger.kernel.org, "David Hildenbrand (Arm)" Subject: Re: [PATCH 4/4] rhashtable: fix vmalloc() deadlock in atomic rehash Message-ID: References: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Nov 04, 2026 at 12:11:24PM +0100, Uladzislau Rezki wrote: > > There are users in kernel. For example: Thanks for the list. > drivers/GPU > /* Allocate the file in vmalloc memory, it's likely to be big */ > iter.start = __vmalloc(file_size, GFP_NOWAIT); > > AMD-GPU: > kvzalloc(size, GFP_NOWAIT); > kvzalloc_objs(struct amdgpu_coredump_ring, GFP_NOWAIT); > kvzalloc(ring->ring_size, GFP_NOWAIT); These appear to be executing out of process context without spin locks so they're not really GFP_ATOMIC. > Virtio ring-testing: > (alloc_ring(0)), gfpflags_allow_blocking(0) does not allow blocking. I didn't really look into this as it's just test code. > net/ipv4/udp.c: > err = bpf_iter_udp_realloc_batch(iter, batch_sks, GFP_NOWAIT); This looks buggy in exactly the same way as rhashtable. It's called under spin_lock_bh, and the same lock can be taken on the softirq path on another CPU. So are there any safe users of kvmalloc with GFP_ATOMIC? If not I suggest that we change kvmalloc to disallow vmalloc when called with GFP_ATOMIC. Thanks, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt