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 E80F142A160 for ; Fri, 24 Jul 2026 11:04:55 +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=1784891098; cv=none; b=t4p9Xg3Mkzf99/ZkwUi6qyPHpEseQHH/PQ3RK7smTYOSxv7lCmRkrfOdmoZWGhy9odnqR9Drazm8RjMy5012gQFdYgLUgHjXX4LDTTGW+G9IvANFB73usj0nxa2wTCkW6mO+yB569jgBmZ/CBiAvRXIFt1/fdGqd7aeFZnNyhuU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784891098; c=relaxed/simple; bh=IAVJz/a6UQd25KugYecHQ4fiJPFojDokUXY41K+jlVc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G7Sxz4IrGGaMv8TBkoBvbCR9aoRqB48jEQmENl4o/L9t6ArnCe3fmUIdVxgNA4JE0OCcatZwez0PtCSyoMMTDs+RCHNb6g1X4QXKdmJ0UftEYKYwUBzlB6zhWjX9L9Qp3xk9Vg/npMjKNtkGPIB/AmJIjun4gJ0Pcrfg2QLU4IY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=I/LVJQhM; 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="I/LVJQhM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA0401F02828; Fri, 24 Jul 2026 11:04:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784891095; bh=3UJNZSYLIJQcwSEZ85YSFQafxQcItdIpWYqrUxCMKlc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=I/LVJQhMkyDUvfnjfKelfZFmNQ1/NhNPV+uexuCzI6g80JkaoVeLcOxEn7C0Z88hd +Xjxlz2O9Wynk43By25A0amGJuTlu7GjggF63+9NbXOGIksz2orVum6q7TAezKifZy e7pJ5QFLoFeiP2x+CWCh7GAdj5F99lO10OVZIEMb2MSr1QfzZmWuuzrZnldK3+/BOz 1MO17kuhA77BXXqFmPQR25R5D36M9oZNDguo3iZS+3igcG8+ZyT3PDAnbM+fiOVWYx 3mLL97qBEKzsVzsAV1b6oLnxDRXDBuL+sVHZjZgDv4ZxyNKpqdcSnajmqCKAsjUmzC GiJRChEfxIgrw== From: Sasha Levin To: stable@vger.kernel.org Cc: Deepanshu Kartikey , syzbot+226c1f947186f8fef796@syzkaller.appspotmail.com, Muchun Song , David Hildenbrand , Oscar Salvador , Mina Almasry , Andrew Morton , Sasha Levin Subject: [PATCH 6.12.y] mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch Date: Fri, 24 Jul 2026 07:00:52 -0400 Message-ID: <20260724110052.3984407-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026072039-endowment-unfazed-086d@gregkh> References: <2026072039-endowment-unfazed-086d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 --- mm/hugetlb.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 17865215fda795..90faa4fd2ca272 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2976,6 +2976,7 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 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 vm_area_struct *vma, 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 vm_area_struct *vma, */ 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 @@ struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma, 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); -- 2.53.0