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 5674E30C166; Fri, 26 Jun 2026 14:57:11 +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=1782485836; cv=none; b=KFoiDYrSTqjOaphLbUxpwTSob6qlHBPyWAhnAUDucdV3nyPxIpvm4Ruu2Ye3KbNox9xsIQCiMK4cnm6yKmrB59Ypq/SBe9vZk0SVof1uqC0sNw2NrxzrRqqUetn9cOcbsI/RRPz1TaGVBMnIuGL/P76QnzlQ6Hg3EoHGuU93q1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782485836; c=relaxed/simple; bh=08SBmbmt1es9nvO/KWBHGxYsF9F9B2UWNxL8xnBLHKM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QF3uo+WEFcbyoXqL51M4nbKG/mbigMYTgd6p8s9Hz8gdh0BRuMCaeMKuLnRd5xhWPlAH19/WvabLlenQCBn0MDhrYlOjLGauNL3O/Q5/SrCA02K4qtKTFUSwp/4U9hGYS1T5F3CfbpwsHF9Moqtc/KwRo+R/bxl7PDZzBMFGPXw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ju6I4k07; 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="Ju6I4k07" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14E031F00A3E; Fri, 26 Jun 2026 14:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782485831; bh=h4dEsq7eT0U+sy2EuGGNHMB1wu+Xu3EYpNjubxVfLcc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Ju6I4k07BJu2QU8MLzI4HFyVkm9JoCqL1MLjMne2NwFtUbN4pZqAK+duO/sguQ1Sm o6SovK2IKQM3F0Un8rewjt0ONXKYPlLEAEE/1Wd3ZmFOZ+Zbwzftm5xGyH9XzqRdRh L87MqYw9nlXGrMJUC2kOD3DCKNhfOI1vxTAW9f7sLsM7xhwUv01IUOWLlzWZ16W0cV AJKwS5fFWuvFPdi5r0qsrkvnNGslW1TXo8gt1tIf7Ds5powFNti/f3BwFEc/rwGh3v rrpok0p8p7P0gG8wWjkKWCW5TzlA8seaPoYHzGbhYd2t4uySesCQye9OQtKfYyKhe1 0nrd4AekvsyQQ== Message-ID: <56b3e774-8866-4e0f-9746-b646a4b58fef@kernel.org> Date: Fri, 26 Jun 2026 16:57:06 +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 RFC 3/4] mm/slab: fix a deadlock in memcg_alloc_abort_single() Content-Language: en-US To: "Harry Yoo (Oracle)" , Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Alexei Starovoitov , Pedro Falcato Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org References: <20260624-kmalloc-nolock-fixes-v1-0-fdf4d17351dd@kernel.org> <20260624-kmalloc-nolock-fixes-v1-3-fdf4d17351dd@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20260624-kmalloc-nolock-fixes-v1-3-fdf4d17351dd@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/24/26 15:11, Harry Yoo (Oracle) wrote: > When kmalloc_nolock() successfully grabs a slab object but memcg aborts > the allocation, the object is freed via __slab_free(). Calling > __slab_free() in unknown context is not allowed and can lead to a > deadlock. > > Free the object via defer_free() when spinning is not allowed. > > Reported-by: Sashiko > Closes: https://sashiko.dev/#/patchset/20260610-slab_alloc_flags-v2-0-7190909db118%40kernel.org?part=9 > Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().") > Cc: stable@vger.kernel.org > Signed-off-by: Harry Yoo (Oracle) Reviewed-by: Vlastimil Babka (SUSE) > --- > mm/slub.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 85760c8ff2e2..4a3618e3967e 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -2459,7 +2459,8 @@ alloc_tagging_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p, > > #ifdef CONFIG_MEMCG > > -static void memcg_alloc_abort_single(struct kmem_cache *s, void *object); > +static void memcg_alloc_abort_single(struct kmem_cache *s, void *object, > + bool allow_spin); > > static __fastpath_inline > bool memcg_slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, > @@ -2477,7 +2478,9 @@ bool memcg_slab_post_alloc_hook(struct kmem_cache *s, gfp_t flags, > return true; > > if (likely(size == 1)) { > - memcg_alloc_abort_single(s, *p); > + bool allow_spin = alloc_flags_allow_spinning(ac->alloc_flags); > + > + memcg_alloc_abort_single(s, *p, allow_spin); > *p = NULL; > } else { > kmem_cache_free_bulk(s, size, p); > @@ -6436,16 +6439,20 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object, > #ifdef CONFIG_MEMCG > /* Do not inline the rare memcg charging failed path into the allocation path */ > static noinline > -void memcg_alloc_abort_single(struct kmem_cache *s, void *object) > +void memcg_alloc_abort_single(struct kmem_cache *s, void *object, bool allow_spin) > { > struct slab *slab = virt_to_slab(object); > bool init = slab_want_init_on_free(s); > - bool allow_spin = true; > > alloc_tagging_slab_free_hook(s, slab, &object, 1); > > - if (likely(slab_free_hook(s, object, init, false, allow_spin))) > + if (unlikely(!slab_free_hook(s, object, init, false, allow_spin))) > + return; > + > + if (likely(allow_spin)) > __slab_free(s, slab, object, object, 1, _RET_IP_); > + else > + defer_free(s, object); > } > #endif > >