From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8882A12E61; Thu, 25 Apr 2024 02:35:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714012522; cv=none; b=e+/LtnXuEZR1O988Eu85CKrM8rzObylOR4BJR51DrmkU4++aE3C/xoIkZ7vOdO2kC3YFDOY3AW8zDEm3HlSXDZCwBz7LTFA9I/QP5NvL/7vVZ+7HbrPaEp0RXfdknxV0SdUuFo+SJUKw5xf56u14yINhDEh+Dx9V6t7WC6OFxgA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714012522; c=relaxed/simple; bh=SYJNkyWVWixL0gc5jowP9EXwnLb+05RTNyJCwACYzrM=; h=Date:To:From:Subject:Message-Id; b=tVKWgZlLCElFCxfKd2D8mTIgZrNPS8PYN5XsPJZKClrQ/LbdCWLampPWEu/CU67s6F5FZFeTXTkZViMSSW01eC6E+iOcwADwfbfvnDFBrW4inEQR3KttIKX46Krem6D5pyKbLd4dLoKImN551r5E2QEG9ZB7Sltsm+6tSTUJcJw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=fTxCveN2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="fTxCveN2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12B98C113CD; Thu, 25 Apr 2024 02:35:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1714012522; bh=SYJNkyWVWixL0gc5jowP9EXwnLb+05RTNyJCwACYzrM=; h=Date:To:From:Subject:From; b=fTxCveN2TqJqnIY6szeCto7QNDgpw/OzEJFEoMU0GhfIX2tW1I/8gJAryUlgjGZFQ sSnXmdm2JGIDnCz+CEXlSlMausOS2eavz4pRTGpGWGN/Wm2MQ2Y8KoJTd0U3qN8z5s FMo7Zde63p1DVjyFVsDVTcvcJmVIK8ZLSsqT50/4= Date: Wed, 24 Apr 2024 19:35:21 -0700 To: mm-commits@vger.kernel.org,yosryahmed@google.com,vitaly.wool@konsulko.com,stable@vger.kernel.org,sjenning@redhat.com,rjones@redhat.com,nphamcs@gmail.com,ddstreet@ieee.org,christian@heusel.eu,chengming.zhou@linux.dev,hannes@cmpxchg.org,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-hotfixes-stable] mm-zswap-fix-shrinker-null-crash-with-cgroup_disable=memory.patch removed from -mm tree Message-Id: <20240425023522.12B98C113CD@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm: zswap: fix shrinker NULL crash with cgroup_disable=memory has been removed from the -mm tree. Its filename was mm-zswap-fix-shrinker-null-crash-with-cgroup_disable=memory.patch This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Johannes Weiner Subject: mm: zswap: fix shrinker NULL crash with cgroup_disable=memory Date: Thu, 18 Apr 2024 08:26:28 -0400 Christian reports a NULL deref in zswap that he bisected down to the zswap shrinker. The issue also cropped up in the bug trackers of libguestfs [1] and the Red Hat bugzilla [2]. The problem is that when memcg is disabled with the boot time flag, the zswap shrinker might get called with sc->memcg == NULL. This is okay in many places, like the lruvec operations. But it crashes in memcg_page_state() - which is only used due to the non-node accounting of cgroup's the zswap memory to begin with. Nhat spotted that the memcg can be NULL in the memcg-disabled case, and I was then able to reproduce the crash locally as well. [1] https://github.com/libguestfs/libguestfs/issues/139 [2] https://bugzilla.redhat.com/show_bug.cgi?id=2275252 Link: https://lkml.kernel.org/r/20240418124043.GC1055428@cmpxchg.org Link: https://lkml.kernel.org/r/20240417143324.GA1055428@cmpxchg.org Fixes: b5ba474f3f51 ("zswap: shrink zswap pool based on memory pressure") Signed-off-by: Johannes Weiner Reported-by: Christian Heusel Debugged-by: Nhat Pham Suggested-by: Nhat Pham Tested-by: Christian Heusel Acked-by: Yosry Ahmed Cc: Chengming Zhou Cc: Dan Streetman Cc: Richard W.M. Jones Cc: Seth Jennings Cc: Vitaly Wool Cc: [v6.8] Signed-off-by: Andrew Morton --- mm/zswap.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) --- a/mm/zswap.c~mm-zswap-fix-shrinker-null-crash-with-cgroup_disable=memory +++ a/mm/zswap.c @@ -1331,15 +1331,22 @@ static unsigned long zswap_shrinker_coun if (!gfp_has_io_fs(sc->gfp_mask)) return 0; -#ifdef CONFIG_MEMCG_KMEM - mem_cgroup_flush_stats(memcg); - nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT; - nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED); -#else - /* use pool stats instead of memcg stats */ - nr_backing = zswap_pool_total_size >> PAGE_SHIFT; - nr_stored = atomic_read(&zswap_nr_stored); -#endif + /* + * For memcg, use the cgroup-wide ZSWAP stats since we don't + * have them per-node and thus per-lruvec. Careful if memcg is + * runtime-disabled: we can get sc->memcg == NULL, which is ok + * for the lruvec, but not for memcg_page_state(). + * + * Without memcg, use the zswap pool-wide metrics. + */ + if (!mem_cgroup_disabled()) { + mem_cgroup_flush_stats(memcg); + nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT; + nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED); + } else { + nr_backing = zswap_pool_total_size >> PAGE_SHIFT; + nr_stored = atomic_read(&zswap_nr_stored); + } if (!nr_stored) return 0; _ Patches currently in -mm which might be from hannes@cmpxchg.org are mm-zswap-optimize-zswap-pool-size-tracking.patch mm-zpool-return-pool-size-in-pages.patch mm-page_alloc-remove-pcppage-migratetype-caching.patch mm-page_alloc-optimize-free_unref_folios.patch mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks.patch mm-page_alloc-move-free-pages-when-converting-block-during-isolation.patch mm-page_alloc-fix-move_freepages_block-range-error.patch mm-page_alloc-fix-freelist-movement-during-block-conversion.patch mm-page_alloc-close-migratetype-race-between-freeing-and-stealing.patch mm-page_isolation-prepare-for-hygienic-freelists.patch mm-page_isolation-prepare-for-hygienic-freelists-fix.patch mm-page_alloc-consolidate-free-page-accounting.patch mm-page_alloc-consolidate-free-page-accounting-fix.patch mm-page_alloc-consolidate-free-page-accounting-fix-2.patch mm-page_alloc-batch-vmstat-updates-in-expand.patch