[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <bdc01d66-01a7-43f6-954f-12a274e294d4@redhat.com>
Date: Fri, 21 Feb 2025 09:12:07 +0100
From: David Hildenbrand <david@...hat.com>
To: Tong Tiangen <tongtiangen@...wei.com>, Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Peter Xu <peterx@...hat.com>,
Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
"Liang, Kan" <kan.liang@...ux.intel.com>,
Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-trace-kernel@...r.kernel.org, bpf@...r.kernel.org,
wangkefeng.wang@...wei.com, Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v2] uprobes: fix two zero old_folio bugs in
__replace_page()
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:
> <TASK>
> 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=@...obe_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
Powered by blists - more mailing lists