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 58BDF316905 for ; Fri, 1 May 2026 19:08:32 +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=1777662512; cv=none; b=lTtXKqnzP/l8UeTMKoSgYesLISwJ1t77fo0gu7czcbF4Clz9bUkZuVCJQ9CJDdpebnvki25jUf7VX50iqvX+eYxMCMHQ7gloDVXLs0ct3uVQ0bJvRPK1iInN5i2RIlAUtmUm5vG25g9OAsyAqwyF6q/4hSRIFHlPkeXO9ZQtadU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777662512; c=relaxed/simple; bh=I6gnZHqYOCIXMIR7WcCKDccSArsK7LaPaWd4F38Mg+c=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Bbor2cVyF3zrwGnu31rj+u2ZPEnYMpnnM93PIMHIXPCs7eKJRwiQkHi9ZILGfo6Ui+60JxgZ1gtVGj1d3clWgbA3MXi3eXgh9qdA1ncFQr1wdk3EKQ7v1IovkcQlWt7dXkvM3upv48JlIZ0VF6SMPjHa5aYUPIJhC6CuioQI4IU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=vCFSKxRu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="vCFSKxRu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2AE8FC2BCB4; Fri, 1 May 2026 19:08:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777662512; bh=I6gnZHqYOCIXMIR7WcCKDccSArsK7LaPaWd4F38Mg+c=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=vCFSKxRu9IyObNQP0Q4c0ohR/O89ev2Mh2lFh4nYXTb4gPMCQcuAv5+UGVP3Y65Rg /6ev2/LxHXqfn6bUirlOeSO9/Xo/yLp3Z2UiHMJ5Ass9u11i6xUrvOJCdua2ir3Jt5 A3AV7cM8wmADSCLkz0kIabN8IZJuAxix3TOaYJhA7YE4KFVjgRF3CI7HPk5LlvTmDK a8vnnEAHM0+4aMN/B5ZGSXSQlnnhnLgfj07OuddnglDg6uoj9GvXW0TH3Y5Exnngn3 LpChLJ4cyBtzbfSHRUBvRAvC2n8aiJk/yD9VS7c0/zAp0UMcYbZKtiwJWm5oGcrgpC Fje7nj6LyeyIg== Message-ID: <24ab5ddc-11a9-40ed-90b2-1a6c68010928@kernel.org> Date: Fri, 1 May 2026 21:08:25 +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 v3] mm/migrate_device: fix pgtable leak in migrate_vma_insert_huge_pmd_page To: Andrew Morton , Sunny Patel Cc: Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Balbir Singh References: <20260501115122.23288-1-nueralspacetech@gmail.com> <20260501054416.af0ed62d635c3eb01d425e61@linux-foundation.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/1/26 14:44, Andrew Morton wrote: > On Fri, 1 May 2026 17:21:16 +0530 Sunny Patel wrote: > >> When migrate_vma_insert_huge_pmd_page() jumps to unlock_abort due >> to a PMD check failure, the pgtable allocated earlier via >> pte_alloc_one() is never freed, causing a memory leak. >> >> Added free_abort label to release the pgtable in error path. >> >> ... >> >> --- a/mm/migrate_device.c >> +++ b/mm/migrate_device.c >> @@ -840,7 +840,7 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, >> } else { >> if (folio_is_zone_device(folio) && >> !folio_is_device_coherent(folio)) { >> - goto abort; >> + goto free_abort; >> } >> entry = folio_mk_pmd(folio, vma->vm_page_prot); >> if (vma->vm_flags & VM_WRITE) >> @@ -893,6 +893,8 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, >> >> unlock_abort: >> spin_unlock(ptl); >> +free_abort: >> + pte_free(vma->vm_mm, pgtable); >> abort: >> for (i = 0; i < HPAGE_PMD_NR; i++) >> src[i] &= ~MIGRATE_PFN_MIGRATE; > > Yikes, we leak that page on several error paths. > > Thanks, I'll retain David's ack from the v2 patch. Yes. If we want to avoid more labels, we could do something like: diff --git a/mm/migrate_device.c b/mm/migrate_device.c index ab49d4dcdb60..babb56c4d47f 100644 --- a/mm/migrate_device.c +++ b/mm/migrate_device.c @@ -795,8 +795,8 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, struct folio *folio = page_folio(page); int ret; vm_fault_t csa_ret; - spinlock_t *ptl; - pgtable_t pgtable; + spinlock_t *ptl = NULL; + pgtable_t pgtable = NULL; pmd_t entry; bool flush = false; unsigned long i; @@ -818,14 +818,14 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, count_vm_event(THP_FAULT_FALLBACK); count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE); ret = -ENOMEM; - goto abort; + goto error; } __folio_mark_uptodate(folio); pgtable = pte_alloc_one(vma->vm_mm); if (unlikely(!pgtable)) - goto abort; + goto error; if (folio_is_device_private(folio)) { swp_entry_t swp_entry; @@ -840,7 +840,7 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, } else { if (folio_is_zone_device(folio) && !folio_is_device_coherent(folio)) { - goto abort; + goto error; } entry = folio_mk_pmd(folio, vma->vm_page_prot); if (vma->vm_flags & VM_WRITE) @@ -850,21 +850,21 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, ptl = pmd_lock(vma->vm_mm, pmdp); csa_ret = check_stable_address_space(vma->vm_mm); if (csa_ret) - goto unlock_abort; + goto error; /* * Check for userfaultfd but do not deliver the fault. Instead, * just back off. */ if (userfaultfd_missing(vma)) - goto unlock_abort; + goto error; if (!pmd_none(*pmdp)) { if (!is_huge_zero_pmd(*pmdp)) - goto unlock_abort; + goto error; flush = true; } else if (!pmd_none(*pmdp)) - goto unlock_abort; + goto error; add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); @@ -891,9 +891,11 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate, return 0; -unlock_abort: - spin_unlock(ptl); -abort: +error: + if (ptl) + spin_unlock(ptl); + if (pgtable) + pte_free(vma->vm_mm, pgtable); for (i = 0; i < HPAGE_PMD_NR; i++) src[i] &= ~MIGRATE_PFN_MIGRATE; return 0; -- Cheers, David