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Tue, 9 Jul 2024 20:07:35 +0800 Subject: Re: [PATCH] mm/hugetlb: fix kernel NULL pointer dereference when migrating hugetlb folio To: , , , CC: , References: <20240709115841.4098393-1-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Tue, 9 Jul 2024 20:07:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20240709115841.4098393-1-linmiaohe@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.127.72] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemd200019.china.huawei.com (7.221.188.193) X-Rspamd-Queue-Id: 1758740012 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 46qo8bbkm5nb9ifu4wsz5qdc76axhmah X-HE-Tag: 1720526860-629724 X-HE-Meta: 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 gBdWP4BE s2KPlQYR1jq22U49uyWMUWck6pybrR6O+VKsw0DvMh3E+IQFt/YYQVVOgBzvsMcTlDHu1TYwGufEbSF7yFLz3c5RPUcq2bzNXssUG8MRHae3o4sfzUAO9YgrwNyuspdxhD3k1lIuTNoot8TyYtMCoQiqT12T/AL7cmYbe7FPGj33eBccqGCqjftZo0/Kjcs0S0OgocKHTePGrtJ823wNbPleXUA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/7/9 19:58, Miaohe Lin wrote: > A kernel crash was observed when migrating hugetlb folio: > > BUG: kernel NULL pointer dereference, address: 0000000000000008 > PGD 0 P4D 0 > Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI > CPU: 0 PID: 3435 Comm: bash Not tainted 6.10.0-rc6-00450-g8578ca01f21f #66 > RIP: 0010:__folio_undo_large_rmappable+0x70/0xb0 > RSP: 0018:ffffb165c98a7b38 EFLAGS: 00000097 > RAX: fffffbbc44528090 RBX: 0000000000000000 RCX: 0000000000000000 > RDX: ffffa30e000a2800 RSI: 0000000000000246 RDI: ffffa3153ffffcc0 > RBP: fffffbbc44528000 R08: 0000000000002371 R09: ffffffffbe4e5868 > R10: 0000000000000001 R11: 0000000000000001 R12: ffffa3153ffffcc0 > R13: fffffbbc44468000 R14: 0000000000000001 R15: 0000000000000001 > FS: 00007f5b3a716740(0000) GS:ffffa3151fc00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000008 CR3: 000000010959a000 CR4: 00000000000006f0 > Call Trace: > > __folio_migrate_mapping+0x59e/0x950 > __migrate_folio.constprop.0+0x5f/0x120 > move_to_new_folio+0xfd/0x250 > migrate_pages+0x383/0xd70 > soft_offline_page+0x2ab/0x7f0 > soft_offline_page_store+0x52/0x90 > kernfs_fop_write_iter+0x12c/0x1d0 > vfs_write+0x380/0x540 > ksys_write+0x64/0xe0 > do_syscall_64+0xb9/0x1d0 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f5b3a514887 > RSP: 002b:00007ffe138fce68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > RAX: ffffffffffffffda RBX: 000000000000000c RCX: 00007f5b3a514887 > RDX: 000000000000000c RSI: 0000556ab809ee10 RDI: 0000000000000001 > RBP: 0000556ab809ee10 R08: 00007f5b3a5d1460 R09: 000000007fffffff > R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000c > R13: 00007f5b3a61b780 R14: 00007f5b3a617600 R15: 00007f5b3a616a00 > > It's because hugetlb folio is passed to __folio_undo_large_rmappable() > unexpectedly. large_rmappable flag is imperceptibly set to hugetlb folio > since commit f6a8dd98a2ce ("hugetlb: convert alloc_buddy_hugetlb_folio to > use a folio"). Then commit be9581ea8c05 ("mm: fix crashes from deferred > split racing folio migration") makes folio_migrate_mapping() call > folio_undo_large_rmappable() triggering the bug. Fix this issue by > clearing large_rmappable flag for hugetlb folios. They don't need that > flag set anyway. > > Fixes: f6a8dd98a2ce ("hugetlb: convert alloc_buddy_hugetlb_folio to use a folio") > Fixes: be9581ea8c05 ("mm: fix crashes from deferred split racing folio migration") > Signed-off-by: Miaohe Lin > Cc: Sorry for make noise. This is not newest version. Will resend soon. Thanks. .