fkie_cve-2021-47531
Vulnerability from fkie_nvd
Published
2024-05-24 15:15
Modified
2024-11-21 06:36
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: drm/msm: Fix mmap to include VM_IO and VM_DONTDUMP In commit 510410bfc034 ("drm/msm: Implement mmap as GEM object function") we switched to a new/cleaner method of doing things. That's good, but we missed a little bit. Before that commit, we used to _first_ run through the drm_gem_mmap_obj() case where `obj->funcs->mmap()` was NULL. That meant that we ran: vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); ...and _then_ we modified those mappings with our own. Now that `obj->funcs->mmap()` is no longer NULL we don't run the default code. It looks like the fact that the vm_flags got VM_IO / VM_DONTDUMP was important because we're now getting crashes on Chromebooks that use ARC++ while logging out. Specifically a crash that looks like this (this is on a 5.10 kernel w/ relevant backports but also seen on a 5.15 kernel): Unable to handle kernel paging request at virtual address ffffffc008000000 Mem abort info: ESR = 0x96000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000008293d000 [ffffffc008000000] pgd=00000001002b3003, p4d=00000001002b3003, pud=00000001002b3003, pmd=0000000000000000 Internal error: Oops: 96000006 [#1] PREEMPT SMP [...] CPU: 7 PID: 15734 Comm: crash_dump64 Tainted: G W 5.10.67 #1 [...] Hardware name: Qualcomm Technologies, Inc. sc7280 IDP SKU2 platform (DT) pstate: 80400009 (Nzcv daif +PAN -UAO -TCO BTYPE=--) pc : __arch_copy_to_user+0xc0/0x30c lr : copyout+0xac/0x14c [...] Call trace: __arch_copy_to_user+0xc0/0x30c copy_page_to_iter+0x1a0/0x294 process_vm_rw_core+0x240/0x408 process_vm_rw+0x110/0x16c __arm64_sys_process_vm_readv+0x30/0x3c el0_svc_common+0xf8/0x250 do_el0_svc+0x30/0x80 el0_svc+0x10/0x1c el0_sync_handler+0x78/0x108 el0_sync+0x184/0x1c0 Code: f8408423 f80008c3 910020c6 36100082 (b8404423) Let's add the two flags back in. While we're at it, the fact that we aren't running the default means that we _don't_ need to clear out VM_PFNMAP, so remove that and save an instruction. NOTE: it was confirmed that VM_IO was the important flag to fix the problem I was seeing, but adding back VM_DONTDUMP seems like a sane thing to do so I'm doing that too.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/3466d9e217b337bf473ee629c608e53f9f3ab786
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8e2b7fe5e8a4be5e571561d9afcfbd92097288ba
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/3466d9e217b337bf473ee629c608e53f9f3ab786
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/8e2b7fe5e8a4be5e571561d9afcfbd92097288ba
Impacted products
Vendor Product Version


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{
   cveTags: [],
   descriptions: [
      {
         lang: "en",
         value: "In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/msm: Fix mmap to include VM_IO and VM_DONTDUMP\n\nIn commit 510410bfc034 (\"drm/msm: Implement mmap as GEM object\nfunction\") we switched to a new/cleaner method of doing things. That's\ngood, but we missed a little bit.\n\nBefore that commit, we used to _first_ run through the\ndrm_gem_mmap_obj() case where `obj->funcs->mmap()` was NULL. That meant\nthat we ran:\n\n  vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;\n  vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));\n  vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);\n\n...and _then_ we modified those mappings with our own. Now that\n`obj->funcs->mmap()` is no longer NULL we don't run the default\ncode. It looks like the fact that the vm_flags got VM_IO / VM_DONTDUMP\nwas important because we're now getting crashes on Chromebooks that\nuse ARC++ while logging out. Specifically a crash that looks like this\n(this is on a 5.10 kernel w/ relevant backports but also seen on a\n5.15 kernel):\n\n  Unable to handle kernel paging request at virtual address ffffffc008000000\n  Mem abort info:\n    ESR = 0x96000006\n    EC = 0x25: DABT (current EL), IL = 32 bits\n    SET = 0, FnV = 0\n    EA = 0, S1PTW = 0\n  Data abort info:\n    ISV = 0, ISS = 0x00000006\n    CM = 0, WnR = 0\n  swapper pgtable: 4k pages, 39-bit VAs, pgdp=000000008293d000\n  [ffffffc008000000] pgd=00000001002b3003, p4d=00000001002b3003,\n                     pud=00000001002b3003, pmd=0000000000000000\n  Internal error: Oops: 96000006 [#1] PREEMPT SMP\n  [...]\n  CPU: 7 PID: 15734 Comm: crash_dump64 Tainted: G W 5.10.67 #1 [...]\n  Hardware name: Qualcomm Technologies, Inc. sc7280 IDP SKU2 platform (DT)\n  pstate: 80400009 (Nzcv daif +PAN -UAO -TCO BTYPE=--)\n  pc : __arch_copy_to_user+0xc0/0x30c\n  lr : copyout+0xac/0x14c\n  [...]\n  Call trace:\n   __arch_copy_to_user+0xc0/0x30c\n   copy_page_to_iter+0x1a0/0x294\n   process_vm_rw_core+0x240/0x408\n   process_vm_rw+0x110/0x16c\n   __arm64_sys_process_vm_readv+0x30/0x3c\n   el0_svc_common+0xf8/0x250\n   do_el0_svc+0x30/0x80\n   el0_svc+0x10/0x1c\n   el0_sync_handler+0x78/0x108\n   el0_sync+0x184/0x1c0\n  Code: f8408423 f80008c3 910020c6 36100082 (b8404423)\n\nLet's add the two flags back in.\n\nWhile we're at it, the fact that we aren't running the default means\nthat we _don't_ need to clear out VM_PFNMAP, so remove that and save\nan instruction.\n\nNOTE: it was confirmed that VM_IO was the important flag to fix the\nproblem I was seeing, but adding back VM_DONTDUMP seems like a sane\nthing to do so I'm doing that too.",
      },
      {
         lang: "es",
         value: "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: drm/msm: corrige mmap para incluir VM_IO y VM_DONTDUMP. En el commit 510410bfc034 (\"drm/msm: implementa mmap como función de objeto GEM\") Nosotros cambiamos a un método nuevo / más limpio de hacer las cosas. Eso es bueno, pero nos perdimos un poquito. Antes de esa confirmación, solíamos ejecutar _primero_ el caso drm_gem_mmap_obj() donde `obj->funcs->mmap()` era NULL. Eso significó que ejecutamos: vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP; vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags)); vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); ...y _luego_ modificamos esas asignaciones con las nuestras. Ahora que `obj->funcs->mmap()` ya no es NULL, no ejecutamos el código predeterminado. Parece que el hecho de que vm_flags obtuviera VM_IO/VM_DONTDUMP fue importante porque ahora estamos teniendo fallas en Chromebooks que usan ARC++ al cerrar sesión. Específicamente, un bloqueo que se ve así (esto ocurre en un kernel 5.10 con backports relevantes, pero también se ve en un kernel 5.15): No se puede manejar la solicitud de paginación del kernel en la dirección virtual ffffffc008000000 Información de cancelación de memoria: ESR = 0x96000006 EC = 0x25: DABT ( EL actual), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Información de cancelación de datos: ISV = 0, ISS = 0x00000006 CM = 0, WnR = 0 tabla de intercambio: 4k páginas, VA de 39 bits , pgdp=000000008293d000 [ffffffc008000000] pgd=00000001002b3003, p4d=00000001002b3003, pud=00000001002b3003, pmd=0000000000000000 Error interno: operaciones: 96000006 [#1] PREEMPT SMP [...] CPU: 7 PID: 15734 Comunicaciones: crash_dump64 Contaminado: GW 5.10.67 #1 [...] Nombre del hardware: Qualcomm Technologies, Inc. sc7280 IDP SKU2 plataforma (DT) pstate: 80400009 (Nzcv daif +PAN -UAO -TCO BTYPE=--) pc: __arch_copy_to_user+0xc0/0x30c lr: copyout+0xac/0x14c [...] Rastreo de llamadas: __arch_copy_to_user+0xc0/0x30c copy_page_to_iter+0x1a0/0x294 Process_vm_rw_core+0x240/0x408 Process_vm_rw+0x110/0x16c __arm64_sys_process_vm_readv+0x30/0 x3c el0_svc_common+0xf8/0x250 do_el0_svc+0x30/0x80 el0_svc+0x10/0x1c el0_sync_handler+0x78/0x108 el0_sync+0x184/0x1c0 Código: f8408423 f80008c3 910020c6 36100082 (b8404423) Agreguemos las dos banderas nuevamente. Mientras estamos en esto, el hecho de que no estemos ejecutando medios predeterminados que _no_ necesitamos borrar VM_PFNMAP, así que elimínelo y guarde una instrucción. NOTA: se confirmó que VM_IO era el indicador importante para solucionar el problema que estaba viendo, pero volver a agregar VM_DONTDUMP parece algo sensato, así que lo estoy haciendo también.",
      },
   ],
   id: "CVE-2021-47531",
   lastModified: "2024-11-21T06:36:28.120",
   metrics: {},
   published: "2024-05-24T15:15:16.357",
   references: [
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         url: "https://git.kernel.org/stable/c/3466d9e217b337bf473ee629c608e53f9f3ab786",
      },
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         url: "https://git.kernel.org/stable/c/8e2b7fe5e8a4be5e571561d9afcfbd92097288ba",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         url: "https://git.kernel.org/stable/c/3466d9e217b337bf473ee629c608e53f9f3ab786",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         url: "https://git.kernel.org/stable/c/8e2b7fe5e8a4be5e571561d9afcfbd92097288ba",
      },
   ],
   sourceIdentifier: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
   vulnStatus: "Awaiting Analysis",
}


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