From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794585543; b=gFg7+bWxianhl0T4QcN05iC5GQEkSkfqXv21wwwO+2ABQItSm2oeos6aDfhJbdAdF6h4 vCnZC+mqU1393N4ZuHe7ndFRzRizu9/CkDW4rYnxU7s1GVQBuxlswQocPU/avwwbGN+Dt bNECH4dM86o1QVsXHnN7BQz0noW1aGXnfenRo6vVjm2XkNYrapXVF19KcGmri7bFA1ab2 mUnWtIde68BfEAf+zyXJD18nxaBgOaODwHoYBYrSObL4N2eJpCTAdkn07utGvEn93niGw smIScZBa5C9myiPC/dzMEi9APhELyW3WhNjy+cm4Yod84j1gn1nOXghlZnsbBuI8Yhg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794585543; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=yAvkyDb/qVlextLvZBgrEg4F6McJuaHfgbLmPG0y5tE=; b=1Fw5QaFcPt07AAzAQt+fP7f513oKAXqVrktUcouNVfQFoQQ2bHuZNe5abf8eqQqh75Uk 6GNbdymhuwL6vD1csSBWfpj81Cz878RQsketaaGmVtrtPBr95WKclVrWe7VoXLZy4K5vU 797zwmRvjB5WeXOFUjWoZ8D4JcITBo/ei7RFdDJkgrA1oe3j5DnpxLLKqGgYHquC8cZuN daM9ON+82C41P+C4yQvOKBIayim2iGlPRIT1D5pyxxdPbzGG3STjlHYhcxUezawRSsYZ9 oDlrDtiERgnVop8InMEhZ9sovqCXokcjN5AYxcrTDIkIkhPnSYle18zYdY1d18ObLIQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=mel+AffR; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5684606A883; Fri, 13 Nov 2026 15:59:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=mel+AffR Received: by smtp.kernel.org (Postfix) with ESMTPSA id E37111F000C6; Fri, 13 Nov 2026 15:59:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794585543; bh=yAvkyDb/qVlextLvZBgrEg4F6McJuaHfgbLmPG0y5tE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=mel+AffRu3OzJB5QfwMNBaz+Acf5mA+WW7X4Qz76tGq1X8aIOO574VkdF/5qeOfCu ZNIi9RL2Zo9rJZU4B+MwydpFPiU/R2tI+MExtRPwsehyCpGt8sdvXn//v0A0kzIeYP /SV70+WbaHWBp+KqH+a6KrsNqWDK4vR9VzXmjS74= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , Rik van Riel , Qi Zheng , Dev Jain , "Lorenzo Stoakes (ARM)" , Kairui Song , Muhammad Usama Anjum , "Harry Yoo (Meta)" , Barry Song , Baolin Wang , Pedro Falcato , "Kiryl Shutsemau (Meta)" , SJ Park , Baoquan He , "David Hildenbrand (Arm)" , Sasha Levin Subject: [PATCH 7.3 145/507] mm/mglru: dont use stack pointers when walking PUD and PMD tables Date: Fri, 13 Nov 2026 10:47:29 -0500 Message-ID: <20261113153759.349146284@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153753.358973689@linuxfoundation.org> References: <20261113153753.358973689@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josef Bacik [ Upstream commit 65a9bf08a3e4d6e58df211ed900c16bafb79b267 ] MGLRU passes stack copies of page-table entries in walk_pud_range() and walk_pmd_range() when walking to the next level. These copies can become stale when khugepaged or MADV_DONTNEED (CONFIG_PT_RECLAIM) removes a PTE table concurrently. This pattern dates back to commit bd74fdaea146 ("mm: multi-gen LRU: support page table walks"). Likely, earlier locking masked the latent bug. Later changes exposed it: commit 1d65b771bc08 ("mm/khugepaged: retract_page_tables() without mmap or vma lock") allowed concurrent retraction, and commit cf4a65539c13 ("memcg-v1: no need for memcg locking for MGLRU") dropped the walker's outer RCU protection. The fix is simple, so just fix the original commit so we don't have to speculate. To fix it, pass the actual PMD/PUD pointers. This restores the RCU-protected lookup and validation against the live PMD. Note that the PUD handling is required as well to handle folded page tables correctly in all cases. Fix generated by an LLM and sent by Josef Bacik in private. [ david: handle walk_pud_range() as well, clarify+simplify description, adjust Fixes: ] Fixes: bd74fdaea146 ("mm: multi-gen LRU: support page table walks") Cc: stable@vger.kernel.org Signed-off-by: Josef Bacik Reviewed-by: Rik van Riel Reviewed-by: Qi Zheng Reviewed-by: Dev Jain Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Kairui Song Tested-by: Muhammad Usama Anjum Reviewed-by: Harry Yoo (Meta) Reviewed-by: Barry Song Reviewed-by: Baolin Wang Reviewed-by: Pedro Falcato Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: SJ Park Link: https://patch.msgid.link/20261031-fixes_core-v3-1-d6437171ecc3@kernel.org Reviewed-by: Baoquan He Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Sasha Levin --- mm/vmscan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 6a53762d55447..963cdd67039d1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3771,7 +3771,7 @@ static void walk_pmd_range(pud_t *pud, unsigned long start, unsigned long end, walk->mm_stats[MM_NONLEAF_FOUND]++; - if (!walk_pte_range(&val, addr, next, args)) + if (!walk_pte_range(pmd + i, addr, next, args)) continue; walk->mm_stats[MM_NONLEAF_ADDED]++; @@ -3807,7 +3807,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end, if (!pud_present(val) || WARN_ON_ONCE(pud_leaf(val))) continue; - walk_pmd_range(&val, addr, next, args); + walk_pmd_range(pud + i, addr, next, args); if (need_resched() || walk->batched >= MAX_LRU_BATCH) { end = (addr | ~PUD_MASK) + 1; -- 2.53.0