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 6801136607D; Thu, 30 Jul 2026 15:52:44 +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=1785426765; cv=none; b=DRMH59S8iihVOu57C1gKd72i57ye2vl5ibY7DJ4GgeKEc2zLmixzAnOFXj63D8FWeoexatL1TJ1CrPjdQLD3nIEELyyIWVMCwWLTJ99qsbfO1HsJVTcLu/QVa7PERqQDOFsVrBq6qmbxbHoICSYL/L0NXsH5tcHwmiG+y0QfoOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785426765; c=relaxed/simple; bh=HPv3bUT0k+nl8/+qrxCJ+1ABuTvZGyuguLCR+kCmwJM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hNAxslU0mlYGG7pDRqpytZ/m+AbMNlaebeZGP/UHuVBbEmWmQGXmg68aoyTzCf1E1the5kalem/WYnvYSIMjb+51tDD5fu6/G9t/kai2O/VTT2webKRgsmc747/e6iYk77xCdPMGaZuKEkalsCs10yvOS5lcePwYRhZBFX4g0I0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=PaR/DGAW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="PaR/DGAW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB8C71F000E9; Thu, 30 Jul 2026 15:52:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785426764; bh=QmV/4CyJb1xun/fYzkeW5OiAiXi4n7YN5SnO18OjuoE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=PaR/DGAWeD1TQt1tc6+ZL47WF5a+cxLwLnjQCOtdX9tGBkQJtVBcMiD51p2TLmZsY Z2hqOzNWCwBQiod0qFv4AJ6Rul+w34g3M+WNi+vbmZPpO5gCDGZSIwdbfLMSB1WiX6 B3u0yGMIsrOYHXqyy7agRf2D1dM/5rX7s/vJ0Q+g= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+226c1f947186f8fef796@syzkaller.appspotmail.com, Deepanshu Kartikey , Muchun Song , David Hildenbrand , Oscar Salvador , Mina Almasry , Andrew Morton , Sasha Levin Subject: [PATCH 6.12 517/602] mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch Date: Thu, 30 Jul 2026 16:15:09 +0200 Message-ID: <20260730141446.868003918@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141435.976815864@linuxfoundation.org> References: <20260730141435.976815864@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Deepanshu Kartikey [ Upstream commit 15807d0ddde37407af72859426b654f3d1972b00 ] In alloc_hugetlb_folio(), a single h_cg pointer is used for both the rsvd and non-rsvd hugetlb cgroup charges. When map_chg is set, hugetlb_cgroup_charge_cgroup_rsvd() stores the charged cgroup in h_cg, but the immediately following hugetlb_cgroup_charge_cgroup() overwrites h_cg with the non-rsvd cgroup pointer. As a result, hugetlb_cgroup_commit_charge_rsvd() stores the wrong (non-rsvd) cgroup pointer into the folio's rsvd slot. When the folio is later freed, free_huge_folio() unconditionally calls both hugetlb_cgroup_uncharge_folio() and hugetlb_cgroup_uncharge_folio_rsvd(). The rsvd uncharge reads back the wrong cgroup from the folio and decrements a counter that was never charged for that cgroup, causing a page_counter underflow: page_counter underflow: -512 nr_pages=512 WARNING: mm/page_counter.c:61 at page_counter_cancel Fix this by introducing a separate h_cg_rsvd pointer exclusively for the rsvd charge path, keeping the rsvd and non-rsvd charges fully independent through their charge, commit, and error uncharge paths. Link: https://lore.kernel.org/20260328065534.346053-1-kartikey406@gmail.com Fixes: 08cf9faf7558 ("hugetlb_cgroup: support noreserve mappings") Reported-by: syzbot+226c1f947186f8fef796@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=226c1f947186f8fef796 Signed-off-by: Deepanshu Kartikey Reviewed-by: Muchun Song Cc: David Hildenbrand Cc: Oscar Salvador Cc: Mina Almasry Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- mm/hugetlb.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2976,6 +2976,7 @@ struct folio *alloc_hugetlb_folio(struct long gbl_chg; int memcg_charge_ret, ret, idx; struct hugetlb_cgroup *h_cg = NULL; + struct hugetlb_cgroup *h_cg_rsvd = NULL; struct mem_cgroup *memcg; bool deferred_reserve; gfp_t gfp = htlb_alloc_mask(h) | __GFP_RETRY_MAYFAIL; @@ -3019,7 +3020,7 @@ struct folio *alloc_hugetlb_folio(struct deferred_reserve = map_chg || avoid_reserve; if (deferred_reserve) { ret = hugetlb_cgroup_charge_cgroup_rsvd( - idx, pages_per_huge_page(h), &h_cg); + idx, pages_per_huge_page(h), &h_cg_rsvd); if (ret) goto out_subpool_put; } @@ -3056,7 +3057,7 @@ struct folio *alloc_hugetlb_folio(struct */ if (deferred_reserve) { hugetlb_cgroup_commit_charge_rsvd(idx, pages_per_huge_page(h), - h_cg, folio); + h_cg_rsvd, folio); } spin_unlock_irq(&hugetlb_lock); @@ -3097,7 +3098,7 @@ out_uncharge_cgroup: out_uncharge_cgroup_reservation: if (deferred_reserve) hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h), - h_cg); + h_cg_rsvd); out_subpool_put: if (map_chg || avoid_reserve) hugepage_subpool_put_pages(spool, 1);