cve-2021-47566
Vulnerability from cvelistv5
Published
2024-05-24 15:12
Modified
2024-12-19 07:44
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: proc/vmcore: fix clearing user buffer by properly using clear_user() To clear a user buffer we cannot simply use memset, we have to use clear_user(). With a virtio-mem device that registers a vmcore_cb and has some logically unplugged memory inside an added Linux memory block, I can easily trigger a BUG by copying the vmcore via "cp": systemd[1]: Starting Kdump Vmcore Save Service... kdump[420]: Kdump is using the default log level(3). kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[465]: saving vmcore-dmesg.txt complete kdump[467]: saving vmcore BUG: unable to handle page fault for address: 00007f2374e01000 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Oops: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86 Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 <49> c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81 RSP: 0018:ffffc9000073be08 EFLAGS: 00010212 RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000 RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008 RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Call Trace: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 ksys_read+0x4f/0xc0 do_syscall_64+0x3b/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae Some x86-64 CPUs have a CPU feature called "Supervisor Mode Access Prevention (SMAP)", which is used to detect wrong access from the kernel to user buffers like this: SMAP triggers a permissions violation on wrong access. In the x86-64 variant of clear_user(), SMAP is properly handled via clac()+stac(). To fix, properly use clear_user() when we're dealing with a user buffer.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/33a7d698f30fa0b99d50569e9909d3baa65d8f6a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/99d348b82bcb36171f24411d3f1a15706a2a937a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9ef384ed300d1bcfb23d0ab0b487d544444d4b52
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a8a917058faf4abaec9fb614bb6d5f8fe3529ec6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a9e164bd160be8cbee1df70acb379129e3cd2e7c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c1e63117711977cc4295b2ce73de29dd17066c82
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/fd7974c547abfb03072a4ee706d3a6f182266f89
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/33a7d698f30fa0b99d50569e9909d3baa65d8f6a
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/99d348b82bcb36171f24411d3f1a15706a2a937a
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/9ef384ed300d1bcfb23d0ab0b487d544444d4b52
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/a8a917058faf4abaec9fb614bb6d5f8fe3529ec6
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/a9e164bd160be8cbee1df70acb379129e3cd2e7c
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/c1e63117711977cc4295b2ce73de29dd17066c82
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/fd7974c547abfb03072a4ee706d3a6f182266f89
Impacted products
Vendor Product Version
Linux Linux Version: 3.0
Show details on NVD website

To clipboard 

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    "nvd": "{\"cve\":{\"id\":\"CVE-2021-47566\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-05-24T15:15:21.637\",\"lastModified\":\"2024-11-21T06:36:34.270\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nproc/vmcore: fix clearing user buffer by properly using clear_user()\\n\\nTo clear a user buffer we cannot simply use memset, we have to use\\nclear_user().  With a virtio-mem device that registers a vmcore_cb and\\nhas some logically unplugged memory inside an added Linux memory block,\\nI can easily trigger a BUG by copying the vmcore via \\\"cp\\\":\\n\\n  systemd[1]: Starting Kdump Vmcore Save Service...\\n  kdump[420]: Kdump is using the default log level(3).\\n  kdump[453]: saving to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/\\n  kdump[458]: saving vmcore-dmesg.txt to /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/\\n  kdump[465]: saving vmcore-dmesg.txt complete\\n  kdump[467]: saving vmcore\\n  BUG: unable to handle page fault for address: 00007f2374e01000\\n  #PF: supervisor write access in kernel mode\\n  #PF: error_code(0x0003) - permissions violation\\n  PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867\\n  Oops: 0003 [#1] PREEMPT SMP NOPTI\\n  CPU: 0 PID: 468 Comm: cp Not tainted 5.15.0+ #6\\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 04/01/2014\\n  RIP: 0010:read_from_oldmem.part.0.cold+0x1d/0x86\\n  Code: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 \u003c49\u003e c7 45 00 00 00 00 00 49 c7 44 05 f8 00 00 00 00 48 83 e7 f81\\n  RSP: 0018:ffffc9000073be08 EFLAGS: 00010212\\n  RAX: 0000000000001000 RBX: 00000000002fd000 RCX: 00007f2374e01000\\n  RDX: 0000000000000001 RSI: 00000000ffffdfff RDI: 00007f2374e01008\\n  RBP: 0000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50\\n  R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000\\n  R13: 00007f2374e01000 R14: 0000000000000000 R15: ffff88807bd421e8\\n  FS:  00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000\\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\n  CR2: 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0\\n  Call Trace:\\n   read_vmcore+0x236/0x2c0\\n   proc_reg_read+0x55/0xa0\\n   vfs_read+0x95/0x190\\n   ksys_read+0x4f/0xc0\\n   do_syscall_64+0x3b/0x90\\n   entry_SYSCALL_64_after_hwframe+0x44/0xae\\n\\nSome x86-64 CPUs have a CPU feature called \\\"Supervisor Mode Access\\nPrevention (SMAP)\\\", which is used to detect wrong access from the kernel\\nto user buffers like this: SMAP triggers a permissions violation on\\nwrong access.  In the x86-64 variant of clear_user(), SMAP is properly\\nhandled via clac()+stac().\\n\\nTo fix, properly use clear_user() when we\u0027re dealing with a user buffer.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: proc/vmcore: corrige el borrado del b\u00fafer del usuario usando correctamente clear_user() Para borrar un b\u00fafer de usuario no podemos simplemente usar memset, tenemos que usar clear_user(). Con un dispositivo virtio-mem que registra un vmcore_cb y tiene algo de memoria l\u00f3gicamente desconectada dentro de un bloque de memoria de Linux agregado, puedo desencadenar f\u00e1cilmente un ERROR copiando el vmcore a trav\u00e9s de \\\"cp\\\": systemd[1]: Iniciando el servicio Kdump Vmcore Save. . kdump[420]: Kdump est\u00e1 utilizando el nivel de registro predeterminado (3). kdump[453]: guardar en /sysroot/var/crash/127.0.0.1-2021-11-11-14:59:22/ kdump[458]: guardar vmcore-dmesg.txt en /sysroot/var/crash/127.0 .0.1-2021-11-11-14:59:22/ kdump[465]: guardar vmcore-dmesg.txt completo kdump[467]: guardar vmcore ERROR: no se puede manejar el error de p\u00e1gina para la direcci\u00f3n: 00007f2374e01000 #PF: escritura del supervisor acceso en modo kernel #PF: error_code(0x0003) - violaci\u00f3n de permisos PGD 7a523067 P4D 7a523067 PUD 7a528067 PMD 7a525067 PTE 800000007048f867 Ups: 0003 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 468 Comm: p No contaminado 5.15.0+ # 6 Nombre del hardware: PC est\u00e1ndar QEMU (Q35 + ICH9, 2009), BIOS rel-1.14.0-27-g64f37cc530f1-prebuilt.qemu.org 01/04/2014 RIP: 0010:read_from_oldmem.part.0.cold+0x1d/ 0x86 C\u00f3digo: ff ff ff e8 05 ff fe ff e9 b9 e9 7f ff 48 89 de 48 c7 c7 38 3b 60 82 e8 f1 fe fe ff 83 fd 08 72 3c 49 8d 7d 08 4c 89 e9 89 e8 \u0026lt;49\u0026gt; c7 45 00 00 00 00 00 49 C7 44 05 F8 00 00 00 00 48 83 E7 F81 RSP: 0018: FFFFFC9000073BE08 EFLAGS: 00010212 RAX: 00000000000000001000 RBX: 000000002FD000 RCX: 00007F2374E RSI: 000000000000FFFFDFFF RDI: 00007F2374E01008 RBP: 000000000000001000 R08: 0000000000000000 R09: ffffc9000073bc50 R10: ffffc9000073bc48 R11: ffffffff829461a8 R12: 000000000000f000 R13: 00007f2374e01000 R14: 0000000000000000 R15: 88807bd421e8 FS: 00007f2374e12140(0000) GS:ffff88807f000000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2 : 00007f2374e01000 CR3: 000000007a4aa000 CR4: 0000000000350eb0 Seguimiento de llamadas: read_vmcore+0x236/0x2c0 proc_reg_read+0x55/0xa0 vfs_read+0x95/0x190 do_syscall_64+0x3b/0x90 Entry_SYSCALL_64_after_hwframe+0x44/0xae Algunas CPU x86-64 tienen una funci\u00f3n de CPU llamada \\\"Prevenci\u00f3n de acceso en modo supervisor (SMAP)\\\", que se utiliza para detectar accesos incorrectos desde el kernel a los b\u00faferes de usuario como este: SMAP desencadena una violaci\u00f3n de permisos en caso de acceso incorrecto. En la variante x86-64 de clear_user(), SMAP se maneja correctamente mediante clac()+stac(). Para solucionarlo, utilice correctamente clear_user() cuando estemos tratando con un b\u00fafer de usuario.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/33a7d698f30fa0b99d50569e9909d3baa65d8f6a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/99d348b82bcb36171f24411d3f1a15706a2a937a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9ef384ed300d1bcfb23d0ab0b487d544444d4b52\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a8a917058faf4abaec9fb614bb6d5f8fe3529ec6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a9e164bd160be8cbee1df70acb379129e3cd2e7c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c1e63117711977cc4295b2ce73de29dd17066c82\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fd7974c547abfb03072a4ee706d3a6f182266f89\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/33a7d698f30fa0b99d50569e9909d3baa65d8f6a\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/99d348b82bcb36171f24411d3f1a15706a2a937a\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/9ef384ed300d1bcfb23d0ab0b487d544444d4b52\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/a8a917058faf4abaec9fb614bb6d5f8fe3529ec6\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/a9e164bd160be8cbee1df70acb379129e3cd2e7c\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/c1e63117711977cc4295b2ce73de29dd17066c82\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"},{\"url\":\"https://git.kernel.org/stable/c/fd7974c547abfb03072a4ee706d3a6f182266f89\",\"source\":\"af854a3a-2127-422b-91ae-364da2661108\"}]}}"
  }
}


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