CVE-2025-21881

一、漏洞信息
 漏洞编号：[CVE-2025-21881](https://nvd.nist.gov/vuln/detail/CVE-2025-21881)
 漏洞归属组件：[kernel](https://gitee.com/src-openeuler/kernel)
 漏洞归属的版本：4.19.140,4.19.194,4.19.90,5.10.0,6.1.19,6.1.8,6.4.0,6.6.0
 CVSS V3.0分值：
  BaseScore：N/A None
  Vector：CVSS：3.0/
 漏洞简述：
  In the Linux kernel, the following vulnerability has been resolved:uprobes: Reject the shared zeropage in uprobe_write_opcode()We triggered the following crash in syzkaller tests:  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:-1The 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 RSScount in mfill_atomic_pte_zeropage() and the refcount of zero folio doesnot increase accordingly. Then, the operation on the same pfn is performedin uprobe_write_opcode()->__replace_page() to unconditional decrease theRSS 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 .There is more, the following warning could also theoretically be triggered:  __replace_page()    -> ...      -> folio_remove_rmap_pte()        -> VM_WARN_ON_FOLIO(is_zero_folio(folio), folio)Considering that uprobe hit on the zero folio is a very rare case, justreject zero old folio immediately after get_user_page_vma_remote().[ mingo: Cleaned up the changelog ]
 漏洞公开时间：2025-03-27 23:15:56
 漏洞创建时间：2025-03-27 23:50:11
 漏洞详情参考链接：
  https://nvd.nist.gov/vuln/detail/CVE-2025-21881
<details>
<summary>更多参考(点击展开)</summary>

| 参考来源 | 参考链接 | 来源链接 |
| ------- | -------- | -------- |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/0b6f19714588cf2366b0364234f97ba963688f63 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/13cca2b73e2b0ec3ea6d6615d615395621d22752 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/54011fc94422f094eaf47555284de70a4bc32bb9 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/bddf10d26e6e5114e7415a0e442ec6f51a559468 |  |
| 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | https://git.kernel.org/stable/c/c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e |  |
| suse_bugzilla | http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2025-21881 | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2025/CVE-2025-21881.mbox | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/stable/c/c4cb2bfa99513311886c1eb5c1c2ac26f3338a6e | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/stable/c/0b6f19714588cf2366b0364234f97ba963688f63 | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/stable/c/13cca2b73e2b0ec3ea6d6615d615395621d22752 | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/stable/c/54011fc94422f094eaf47555284de70a4bc32bb9 | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| suse_bugzilla | https://git.kernel.org/stable/c/bddf10d26e6e5114e7415a0e442ec6f51a559468 | https://bugzilla.suse.com/show_bug.cgi?id=1240185 |
| redhat_bugzilla | https://lore.kernel.org/linux-cve-announce/2025032712-CVE-2025-21881-7a0f@gregkh/T | https://bugzilla.redhat.com/show_bug.cgi?id=2355422 |
| redhat_bugzilla | https://lore.kernel.org/linux-cve-announce/2025032712-CVE-2025-21881-7a0f@gregkh/T | https://bugzilla.redhat.com/show_bug.cgi?id=2355422 |
| anolis |  | https://anas.openanolis.cn/cves/detail/CVE-2025-21881 |

</details>

漏洞分析指导链接：
  https://gitee.com/openeuler/cve-manager/blob/master/cve-vulner-manager/doc/md/manual.md
 漏洞数据来源:
  openBrain开源漏洞感知系统
 漏洞补丁信息：
  <details>
<summary>详情(点击展开)</summary>

| 影响的包 | 修复版本 | 修复补丁 | 问题引入补丁 | 来源  |
| ------- | -------- | ------- | -------- | --------- |
| linux_kernel | 6.1.130 | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c4cb2bfa99513311886c1eb5c1c2ac26f3338a6eIssue | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b144498350860b6ee9dc57ff27a93ad488de5dc | linuxkernelcves |
| linux_kernel | 6.6.81 | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0b6f19714588cf2366b0364234f97ba963688f63Issue | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b144498350860b6ee9dc57ff27a93ad488de5dc | linuxkernelcves |
| linux_kernel | 6.12.18 | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13cca2b73e2b0ec3ea6d6615d615395621d22752Issue | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b144498350860b6ee9dc57ff27a93ad488de5dc | linuxkernelcves |
| linux_kernel | 6.13.6 | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=54011fc94422f094eaf47555284de70a4bc32bb9Issue | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b144498350860b6ee9dc57ff27a93ad488de5dc | linuxkernelcves |
| linux_kernel | 6.14 | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bddf10d26e6e5114e7415a0e442ec6f51a559468Please | https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b144498350860b6ee9dc57ff27a93ad488de5dc | linuxkernelcves |

</details>

二、漏洞分析结构反馈
 影响性分析说明：
  In the Linux kernel, the following vulnerability has been resolved:uprobes: Reject the shared zeropage in uprobe_write_opcode()We triggered the following crash in syzkaller tests:  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:   &lt;TASK&gt;   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:-1The following syzkaller test case can be used to reproduce:  r2 = creat(&#38;(0x7f0000000000)=&#39;./file0 x00&#39;, 0x8)  write$nbd(r2, &#38;(0x7f0000000580)=ANY=[], 0x10)  r4 = openat(0xffffffffffffff9c, &#38;(0x7f0000000040)=&#39;./file0 x00&#39;, 0x42, 0x0)  mmap$IORING_OFF_SQ_RING(&#38;(0x7f0000ffd000/0x3000)=nil, 0x3000, 0x0, 0x12, r4, 0x0)  r5 = userfaultfd(0x80801)  ioctl$UFFDIO_API(r5, 0xc018aa3f, &#38;(0x7f0000000040)={0xaa, 0x20})  r6 = userfaultfd(0x80801)  ioctl$UFFDIO_API(r6, 0xc018aa3f, &#38;(0x7f0000000140))  ioctl$UFFDIO_REGISTER(r6, 0xc020aa00, &#38;(0x7f0000000100)={{&#38;(0x7f0000ffc000/0x4000)=nil, 0x4000}, 0x2})  ioctl$UFFDIO_ZEROPAGE(r5, 0xc020aa04, &#38;(0x7f0000000000)={{&#38;(0x7f0000ffd000/0x1000)=nil, 0x1000}})  r7 = bpf$PROG_LOAD(0x5, &#38;(0x7f0000000140)={0x2, 0x3, &#38;(0x7f0000000200)=ANY=[@ANYBLOB=&#34;1800000000120000000000000000000095&#34;], &#38;(0x7f0000000000)=&#39;GPL x00&#39;, 0x7, 0x0, 0x0, 0x0, 0x0, &#39; x00&#39;, 0x0, @fallback=0x30, 0xffffffffffffffff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x10, 0x0, @void, @value}, 0x94)  bpf$BPF_LINK_CREATE_XDP(0x1c, &#38;(0x7f0000000040)={r7, 0x0, 0x30, 0x1e, @val=@uprobe_multi={&#38;(0x7f0000000080)=&#39;./file0 x00&#39;, &#38;(0x7f0000000100)=[0x2], 0x0, 0x0, 0x1}}, 0x40)The cause is that zero pfn is set to the PTE without increasing the RSScount in mfill_atomic_pte_zeropage() and the refcount of zero folio doesnot increase accordingly. Then, the operation on the same pfn is performedin uprobe_write_opcode()-&gt;__replace_page() to unconditional decrease theRSS count and old_folio&#39;s refcount.Therefore, two bugs are introduced: 1. The RSS count is incorrect, when process exit, the check_mm() report    error &#34;Bad rss-count&#34;. 2. The reserved folio (zero folio) is freed when folio-&gt;refcount is zero,    then free_pages_prepare-&gt;free_page_is_bad() report error    &#34;Bad page state&#34;.There is more, the following warning could also theoretically be triggered:  __replace_page()    -&gt; ...      -&gt; folio_remove_rmap_pte()        -&gt; VM_WARN_ON_FOLIO(is_zero_folio(folio), folio)Considering that uprobe hit on the zero folio is a very rare case, justreject zero old folio immediately after get_user_page_vma_remote().[ mingo: Cleaned up the changelog ]The Linux kernel CVE team has assigned CVE-2025-21881 to this issue.
 openEuler评分：
  3.9
 Vector：CVSS：3.0/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:L
 受影响版本排查(受影响/不受影响)：
  1.openEuler-20.03-LTS-SP4(4.19.90):受影响
2.openEuler-22.03-LTS-SP3(5.10.0):受影响
3.openEuler-22.03-LTS-SP4(5.10.0):受影响
4.openEuler-24.03-LTS(6.6.0):受影响
5.openEuler-24.03-LTS-SP1(6.6.0):受影响
6.master(6.6.0):不受影响
7.openEuler-24.03-LTS-Next(6.6.0):不受影响

修复是否涉及abi变化(是/否)：
  1.master(6.6.0):否
2.openEuler-20.03-LTS-SP4(4.19.90):否
3.openEuler-22.03-LTS-SP3(5.10.0):否
4.openEuler-22.03-LTS-SP4(5.10.0):否
5.openEuler-24.03-LTS(6.6.0):否
6.openEuler-24.03-LTS-Next(6.6.0):否
7.openEuler-24.03-LTS-SP1(6.6.0):否

原因说明：
  1.openEuler-22.03-LTS-SP3(5.10.0):正常修复
2.openEuler-22.03-LTS-SP4(5.10.0):正常修复
3.openEuler-24.03-LTS(6.6.0):正常修复
4.openEuler-24.03-LTS-SP1(6.6.0):正常修复
5.openEuler-20.03-LTS-SP4(4.19.90):不修复-超出修复范围
6.master(6.6.0):不受影响-漏洞代码不能被攻击者触发
7.openEuler-24.03-LTS-Next(6.6.0):不受影响-漏洞代码不能被攻击者触发

三、漏洞修复
安全公告链接：https://www.openeuler.org/zh/security/safety-bulletin/detail/?id=openEuler-SA-2025-1450

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