CVE-2024-40955

{"id": "CVE-2024-40955", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.5, "attackVector": "LOCAL", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.8}]}, "published": "2024-07-12T13:15:17.697", "references": [{"url": "https://git.kernel.org/stable/c/13df4d44a3aaabe61cd01d277b6ee23ead2a5206", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/677ff4589f1501578fa903a25bb14831d0607992", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/b829687ae1229224262bcabf49accfa2dbf8db06", "tags": ["Patch"], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "nvd@nist.gov", "description": [{"lang": "en", "value": "CWE-787"}]}], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists()\n\nWe can trigger a slab-out-of-bounds with the following commands:\n\n mkfs.ext4 -F /dev/$disk 10G\n mount /dev/$disk /tmp/test\n echo 2147483647 > /sys/fs/ext4/$disk/mb_group_prealloc\n echo test > /tmp/test/file && sync\n\n==================================================================\nBUG: KASAN: slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4]\nRead of size 8 at addr ffff888121b9d0f0 by task kworker/u2:0/11\nCPU: 0 PID: 11 Comm: kworker/u2:0 Tainted: GL 6.7.0-next-20240118 #521\nCall Trace:\n dump_stack_lvl+0x2c/0x50\n kasan_report+0xb6/0xf0\n ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4]\n ext4_mb_regular_allocator+0x19e9/0x2370 [ext4]\n ext4_mb_new_blocks+0x88a/0x1370 [ext4]\n ext4_ext_map_blocks+0x14f7/0x2390 [ext4]\n ext4_map_blocks+0x569/0xea0 [ext4]\n ext4_do_writepages+0x10f6/0x1bc0 [ext4]\n[...]\n==================================================================\n\nThe flow of issue triggering is as follows:\n\n// Set s_mb_group_prealloc to 2147483647 via sysfs\next4_mb_new_blocks\n ext4_mb_normalize_request\n ext4_mb_normalize_group_request\n ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc\n ext4_mb_regular_allocator\n ext4_mb_choose_next_group\n ext4_mb_choose_next_group_best_avail\n mb_avg_fragment_size_order\n order = fls(len) - 2 = 29\n ext4_mb_find_good_group_avg_frag_lists\n frag_list = &sbi->s_mb_avg_fragment_size[order]\n if (list_empty(frag_list)) // Trigger SOOB!\n\nAt 4k block size, the length of the s_mb_avg_fragment_size list is 14,\nbut an oversized s_mb_group_prealloc is set, causing slab-out-of-bounds\nto be triggered by an attempt to access an element at index 29.\n\nAdd a new attr_id attr_clusters_in_group with values in the range\n[0, sbi->s_clusters_per_group] and declare mb_group_prealloc as\nthat type to fix the issue. In addition avoid returning an order\nfrom mb_avg_fragment_size_order() greater than MB_NUM_ORDERS(sb)\nand reduce some useless loops."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ext4: arreglar slab-out-of-bounds en ext4_mb_find_good_group_avg_frag_lists() Podemos activar un slab-out-of-bounds con los siguientes comandos: mkfs.ext4 -F /dev/ $disk 10G montaje /dev/$disk /tmp/test echo 2147483647 > /sys/fs/ext4/$disk/mb_group_prealloc echo test > /tmp/test/file && sync ============ ==================================================== ==== ERROR: KASAN: losa fuera de los l\u00edmites en ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4] Lectura de tama\u00f1o 8 en la direcci\u00f3n ffff888121b9d0f0 por tarea kworker/u2:0/11 CPU: 0 PID: 11 Comm: kworker/ u2:0 Tainted: GL 6.7.0-next-20240118 #521 Seguimiento de llamadas: dump_stack_lvl+0x2c/0x50 kasan_report+0xb6/0xf0 ext4_mb_find_good_group_avg_frag_lists+0x8a/0x200 [ext4_mb_regular_allocator+0x19e9 /0x2370 [ext4] text4_mb_new_blocks+0x88a/0x1370 [ text4] text4_ext_map_blocks+0x14f7/0x2390 [ext4] text4_map_blocks+0x569/0xea0 [ext4] text4_do_writepages+0x10f6/0x1bc0 [ext4] [...] ==================== ================================================ El flujo de La activaci\u00f3n del problema es la siguiente: // Establezca s_mb_group_prealloc en 2147483647 a trav\u00e9s de sysfs ext4_mb_new_blocks ext4_mb_normalize_request ext4_mb_normalize_group_request ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc ext4_mb_regular_allocator ext4_mb_choose _next_group ext4_mb_choose_next_group_best_avail mb_avg_fragment_size_order orden = fls(len) - 2 = 29 ext4_mb_find_good_group_avg_frag_lists frag_list = &sbi- >s_mb_avg_fragment_size[order] if (list_empty(frag_list)) // \u00a1Activa SOOB! En un tama\u00f1o de bloque de 4k, la longitud de la lista s_mb_avg_fragment_size es 14, pero se establece un s_mb_group_prealloc de gran tama\u00f1o, lo que provoca que los l\u00edmites de losa se activen al intentar acceder a un elemento en el \u00edndice 29. Agregue un nuevo attr_id attr_clusters_in_group con valores en el rango [0, sbi->s_clusters_per_group] y declare mb_group_prealloc como ese tipo para solucionar el problema. Adem\u00e1s, evite devolver un pedido de mb_avg_fragment_size_order() mayor que MB_NUM_ORDERS(sb) y reduzca algunos bucles in\u00fatiles."}], "lastModified": "2024-08-28T19:45:37.080", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "A9A441DF-0244-4D7F-B25A-F692568FFC15", "versionEndExcluding": "6.6.36", "versionStartIncluding": "6.5"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "0A047AF2-94AC-4A3A-B32D-6AB930D8EF1C", "versionEndExcluding": "6.9.7", "versionStartIncluding": "6.7"}], "operator": "OR"}]}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}