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Message-Id: <20250805035447.7958-1-21cnbao@gmail.com>
Date: Tue, 5 Aug 2025 11:54:47 +0800
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
Barry Song <v-songbaohua@...o.com>,
"Lai, Yi" <yi1.lai@...ux.intel.com>,
David Hildenbrand <david@...hat.com>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Qi Zheng <zhengqi.arch@...edance.com>,
Vlastimil Babka <vbabka@...e.cz>,
Jann Horn <jannh@...gle.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Lokesh Gidra <lokeshgidra@...gle.com>,
Tangquan Zheng <zhengtangquan@...o.com>,
Lance Yang <ioworker0@...il.com>,
Zi Yan <ziy@...dia.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
"Liam R . Howlett" <Liam.Howlett@...cle.com>,
Nico Pache <npache@...hat.com>,
Ryan Roberts <ryan.roberts@....com>,
Dev Jain <dev.jain@....com>
Subject: [PATCH] mm: Fix the race between collapse and PT_RECLAIM under per-vma lock
From: Barry Song <v-songbaohua@...o.com>
The check_pmd_still_valid() call during collapse is currently only
protected by the mmap_lock in write mode, which was sufficient when
pt_reclaim always ran under mmap_lock in read mode. However, since
madvise_dontneed can now execute under a per-VMA lock, this assumption
is no longer valid. As a result, a race condition can occur between
collapse and PT_RECLAIM, potentially leading to a kernel panic.
[ 38.151897] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASI
[ 38.153519] KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
[ 38.154605] CPU: 0 UID: 0 PID: 721 Comm: repro Not tainted 6.16.0-next-20250801-next-2025080 #1 PREEMPT(voluntary)
[ 38.155929] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org4
[ 38.157418] RIP: 0010:kasan_byte_accessible+0x15/0x30
[ 38.158125] Code: 03 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 b8 00 00 00 00 00 fc0
[ 38.160461] RSP: 0018:ffff88800feef678 EFLAGS: 00010286
[ 38.161220] RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 1ffffffff0dde60c
[ 38.162232] RDX: 0000000000000000 RSI: ffffffff85da1e18 RDI: dffffc0000000003
[ 38.163176] RBP: ffff88800feef698 R08: 0000000000000001 R09: 0000000000000000
[ 38.164195] R10: 0000000000000000 R11: ffff888016a8ba58 R12: 0000000000000018
[ 38.165189] R13: 0000000000000018 R14: ffffffff85da1e18 R15: 0000000000000000
[ 38.166100] FS: 0000000000000000(0000) GS:ffff8880e3b40000(0000) knlGS:0000000000000000
[ 38.167137] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 38.167891] CR2: 00007f97fadfe504 CR3: 0000000007088005 CR4: 0000000000770ef0
[ 38.168812] PKRU: 55555554
[ 38.169275] Call Trace:
[ 38.169647] <TASK>
[ 38.169975] ? __kasan_check_byte+0x19/0x50
[ 38.170581] lock_acquire+0xea/0x310
[ 38.171083] ? rcu_is_watching+0x19/0xc0
[ 38.171615] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
[ 38.172343] ? __sanitizer_cov_trace_const_cmp8+0x1c/0x30
[ 38.173130] _raw_spin_lock+0x38/0x50
[ 38.173707] ? __pte_offset_map_lock+0x1a2/0x3c0
[ 38.174390] __pte_offset_map_lock+0x1a2/0x3c0
[ 38.174987] ? __pfx___pte_offset_map_lock+0x10/0x10
[ 38.175724] ? __pfx_pud_val+0x10/0x10
[ 38.176308] ? __sanitizer_cov_trace_const_cmp1+0x1e/0x30
[ 38.177183] unmap_page_range+0xb60/0x43e0
[ 38.177824] ? __pfx_unmap_page_range+0x10/0x10
[ 38.178485] ? mas_next_slot+0x133a/0x1a50
[ 38.179079] unmap_single_vma.constprop.0+0x15b/0x250
[ 38.179830] unmap_vmas+0x1fa/0x460
[ 38.180373] ? __pfx_unmap_vmas+0x10/0x10
[ 38.180994] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20
[ 38.181877] exit_mmap+0x1a2/0xb40
[ 38.182396] ? lock_release+0x14f/0x2c0
[ 38.182929] ? __pfx_exit_mmap+0x10/0x10
[ 38.183474] ? __pfx___mutex_unlock_slowpath+0x10/0x10
[ 38.184188] ? mutex_unlock+0x16/0x20
[ 38.184704] mmput+0x132/0x370
[ 38.185208] do_exit+0x7e7/0x28c0
[ 38.185682] ? __this_cpu_preempt_check+0x21/0x30
[ 38.186328] ? do_group_exit+0x1d8/0x2c0
[ 38.186873] ? __pfx_do_exit+0x10/0x10
[ 38.187401] ? __this_cpu_preempt_check+0x21/0x30
[ 38.188036] ? _raw_spin_unlock_irq+0x2c/0x60
[ 38.188634] ? lockdep_hardirqs_on+0x89/0x110
[ 38.189313] do_group_exit+0xe4/0x2c0
[ 38.189831] __x64_sys_exit_group+0x4d/0x60
[ 38.190413] x64_sys_call+0x2174/0x2180
[ 38.190935] do_syscall_64+0x6d/0x2e0
[ 38.191449] entry_SYSCALL_64_after_hwframe+0x76/0x7e
This patch moves the vma_start_write() call to precede
check_pmd_still_valid(), ensuring that the check is also properly
protected by the per-VMA lock.
Fixes: a6fde7add78d ("mm: use per_vma lock for MADV_DONTNEED")
Tested-by: "Lai, Yi" <yi1.lai@...ux.intel.com>
Reported-by: "Lai, Yi" <yi1.lai@...ux.intel.com>
Closes: https://lore.kernel.org/all/aJAFrYfyzGpbm+0m@ly-workstation/
Cc: David Hildenbrand <david@...hat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Qi Zheng <zhengqi.arch@...edance.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Jann Horn <jannh@...gle.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Cc: Lokesh Gidra <lokeshgidra@...gle.com>
Cc: Tangquan Zheng <zhengtangquan@...o.com>
Cc: Lance Yang <ioworker0@...il.com>
Cc: Zi Yan <ziy@...dia.com>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: Liam R. Howlett <Liam.Howlett@...cle.com>
Cc: Nico Pache <npache@...hat.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Dev Jain <dev.jain@....com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
mm/khugepaged.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 374a6a5193a7..6b40bdfd224c 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1172,11 +1172,11 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
if (result != SCAN_SUCCEED)
goto out_up_write;
/* check if the pmd is still valid */
+ vma_start_write(vma);
result = check_pmd_still_valid(mm, address, pmd);
if (result != SCAN_SUCCEED)
goto out_up_write;
- vma_start_write(vma);
anon_vma_lock_write(vma->anon_vma);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address,
--
2.39.3 (Apple Git-146)
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