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[79.242.56.144]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-439b02ce404sm9811415e9.7.2025.02.21.00.12.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Feb 2025 00:12:09 -0800 (PST) Message-ID: Date: Fri, 21 Feb 2025 09:12:07 +0100 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next v2] uprobes: fix two zero old_folio bugs in __replace_page() To: Tong Tiangen , Oleg Nesterov , Andrew Morton , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Peter Xu , Ian Rogers , Adrian Hunter , "Liang, Kan" , Masami Hiramatsu Cc: linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, wangkefeng.wang@huawei.com, Guohanjun References: <20250221015056.1269344-1-tongtiangen@huawei.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.02.25 02:50, Tong Tiangen wrote: > We triggered the following error logs in syzkaller test: > > BUG: Bad page state in process syz.7.38 pfn:1eff3 > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1eff3 > flags: 0x3fffff00004004(referenced|reserved|node=0|zone=1|lastcpupid=0x1fffff) > raw: 003fffff00004004 ffffe6c6c07bfcc8 ffffe6c6c07bfcc8 0000000000000000 > raw: 0000000000000000 0000000000000000 00000000fffffffe 0000000000000000 > page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > Call Trace: > > dump_stack_lvl+0x32/0x50 > bad_page+0x69/0xf0 > free_unref_page_prepare+0x401/0x500 > free_unref_page+0x6d/0x1b0 > uprobe_write_opcode+0x460/0x8e0 > install_breakpoint.part.0+0x51/0x80 > register_for_each_vma+0x1d9/0x2b0 > __uprobe_register+0x245/0x300 > bpf_uprobe_multi_link_attach+0x29b/0x4f0 > link_create+0x1e2/0x280 > __sys_bpf+0x75f/0xac0 > __x64_sys_bpf+0x1a/0x30 > do_syscall_64+0x56/0x100 > entry_SYSCALL_64_after_hwframe+0x78/0xe2 > > BUG: Bad rss-counter state mm:00000000452453e0 type:MM_FILEPAGES val:-1 > > The following syzkaller test case can be used to reproduce: > > r2 = creat(&(0x7f0000000000)='./file0\x00', 0x8) > write$nbd(r2, &(0x7f0000000580)=ANY=[], 0x10) > r4 = openat(0xffffffffffffff9c, &(0x7f0000000040)='./file0\x00', 0x42, 0x0) > mmap$IORING_OFF_SQ_RING(&(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0) > r5 = userfaultfd(0x80801) > ioctl$UFFDIO_API(r5, 0xc018aa3f, &(0x7f0000000040)={0xaa, 0x20}) > r6 = userfaultfd(0x80801) > ioctl$UFFDIO_API(r6, 0xc018aa3f, &(0x7f0000000140)) > ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &(0x7f0000000100)={{&(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2}) > ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &(0x7f0000000000)={{&(0x7f0000ffd000/0x1000)=nil, 0x1000}}) > r7 = bpf$PROG_LOAD(0x5, &(0x7f0000000140)={0x2, 0x3, &(0x7f0000000200)=ANY=[@ANYBLOB="1800000000120000000000000000000095"], &(0x7f0000000000)='GPL\x00', 0x7, 0x0, 0x0, 0x0, 0x0, '\x00', 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94) > bpf$BPF_LINK_CREATE_XDP(0x1c, &(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&(0x7f0000000080)='./file0\x00', &(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40) > > The cause is that zero pfn is set to the pte without increasing the rss > count in mfill_atomic_pte_zeropage() and the refcount of zero folio does > not increase accordingly. Then, the operation on the same pfn is performed > in uprobe_write_opcode()->__replace_page() to unconditional decrease the > rss count and old_folio's refcount. > > Therefore, two bugs are introduced: > 1. The rss count is incorrect, when process exit, the check_mm() report > error "Bad rss-count". > 2. The reserved folio (zero folio) is freed when folio->refcount is zero, > then free_pages_prepare->free_page_is_bad() report error > "Bad page state". Well, there is more, like triggering the VM_WARN_ON_FOLIO(is_zero_folio(folio), folio); in __folio_rmap_sanity_checks() I assume. So maybe just call the patch "uprobes: reject the share zeropage in uprobe_write_opcode)()" Thanks! -- Cheers, David / dhildenb