linux-kernel - [PATCH] mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250121200929.188542-1-roman.gushchin@linux.dev>
Date: Tue, 21 Jan 2025 20:09:29 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Jann Horn <jannh@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Will Deacon <will@...nel.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	Nick Piggin <npiggin@...il.com>,
	Hugh Dickins <hughd@...gle.com>,
	linux-arch@...r.kernel.org
Subject: [PATCH] mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free_pgtables()

Commit b67fbebd4cf9 ("mmu_gather: Force tlb-flush VM_PFNMAP vmas")
added a forced tlbflush to tlb_vma_end(), which is required to avoid a
race between munmap() and unmap_mapping_range(). However it added some
overhead to other paths where tlb_vma_end() is used, but vmas are not
removed, e.g. madvise(MADV_DONTNEED).

Fix this by moving the tlb flush out of tlb_end_vma() into
free_pgtables(), somewhat similar to the stable version of the
original commit: e.g. stable commit 895428ee124a ("mm: Force TLB flush
for PFNMAP mappings before unlink_file_vma()").

Note, that if tlb->fullmm is set, no flush is required, as the whole
mm is about to be destroyed.

Suggested-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Nick Piggin <npiggin@...il.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: linux-arch@...r.kernel.org
Cc: linux-mm@...ck.org
---
 include/asm-generic/tlb.h | 16 ++++------------
 mm/memory.c               |  7 +++++++
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 709830274b75..411daa96f57a 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -549,22 +549,14 @@ static inline void tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *
 
 static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 {
-	if (tlb->fullmm)
+	if (tlb->fullmm || IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS))
 		return;
 
 	/*
-	 * VM_PFNMAP is more fragile because the core mm will not track the
-	 * page mapcount -- there might not be page-frames for these PFNs after
-	 * all. Force flush TLBs for such ranges to avoid munmap() vs
-	 * unmap_mapping_range() races.
+	 * Do a TLB flush and reset the range at VMA boundaries; this avoids
+	 * the ranges growing with the unused space between consecutive VMAs.
 	 */
-	if (tlb->vma_pfn || !IS_ENABLED(CONFIG_MMU_GATHER_MERGE_VMAS)) {
-		/*
-		 * Do a TLB flush and reset the range at VMA boundaries; this avoids
-		 * the ranges growing with the unused space between consecutive VMAs.
-		 */
-		tlb_flush_mmu_tlbonly(tlb);
-	}
+	tlb_flush_mmu_tlbonly(tlb);
 }
 
 /*
diff --git a/mm/memory.c b/mm/memory.c
index 398c031be9ba..2071415f68dd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -365,6 +365,13 @@ void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas,
 {
 	struct unlink_vma_file_batch vb;
 
+	/*
+	 * Ensure we have no stale TLB entries by the time this mapping is
+	 * removed from the rmap.
+	 */
+	if (tlb->vma_pfn && !tlb->fullmm)
+		tlb_flush_mmu(tlb);
+
 	do {
 		unsigned long addr = vma->vm_start;
 		struct vm_area_struct *next;
-- 
2.48.0.rc2.279.g1de40edade-goog