CVE-2023-53143 (GCVE-0-2023-53143)

Vulnerability from cvelistv5 – Published: 2025-05-02 15:56 – Updated: 2025-05-04 07:50
VLAI?
Title
ext4: fix another off-by-one fsmap error on 1k block filesystems
Summary
In the Linux kernel, the following vulnerability has been resolved: ext4: fix another off-by-one fsmap error on 1k block filesystems Apparently syzbot figured out that issuing this FSMAP call: struct fsmap_head cmd = { .fmh_count = ...; .fmh_keys = { { .fmr_device = /* ext4 dev */, .fmr_physical = 0, }, { .fmr_device = /* ext4 dev */, .fmr_physical = 0, }, }, ... }; ret = ioctl(fd, FS_IOC_GETFSMAP, &cmd); Produces this crash if the underlying filesystem is a 1k-block ext4 filesystem: kernel BUG at fs/ext4/ext4.h:3331! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 3 PID: 3227965 Comm: xfs_io Tainted: G W O 6.2.0-rc8-achx Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:ext4_mb_load_buddy_gfp+0x47c/0x570 [ext4] RSP: 0018:ffffc90007c03998 EFLAGS: 00010246 RAX: ffff888004978000 RBX: ffffc90007c03a20 RCX: ffff888041618000 RDX: 0000000000000000 RSI: 00000000000005a4 RDI: ffffffffa0c99b11 RBP: ffff888012330000 R08: ffffffffa0c2b7d0 R09: 0000000000000400 R10: ffffc90007c03950 R11: 0000000000000000 R12: 0000000000000001 R13: 00000000ffffffff R14: 0000000000000c40 R15: ffff88802678c398 FS: 00007fdf2020c880(0000) GS:ffff88807e100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffd318a5fe8 CR3: 000000007f80f001 CR4: 00000000001706e0 Call Trace: <TASK> ext4_mballoc_query_range+0x4b/0x210 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_getfsmap_datadev+0x713/0x890 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_getfsmap+0x2b7/0x330 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] ext4_ioc_getfsmap+0x153/0x2b0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] __ext4_ioctl+0x2a7/0x17e0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80] __x64_sys_ioctl+0x82/0xa0 do_syscall_64+0x2b/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7fdf20558aff RSP: 002b:00007ffd318a9e30 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000000200c0 RCX: 00007fdf20558aff RDX: 00007fdf1feb2010 RSI: 00000000c0c0583b RDI: 0000000000000003 RBP: 00005625c0634be0 R08: 00005625c0634c40 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fdf1feb2010 R13: 00005625be70d994 R14: 0000000000000800 R15: 0000000000000000 For GETFSMAP calls, the caller selects a physical block device by writing its block number into fsmap_head.fmh_keys[01].fmr_device. To query mappings for a subrange of the device, the starting byte of the range is written to fsmap_head.fmh_keys[0].fmr_physical and the last byte of the range goes in fsmap_head.fmh_keys[1].fmr_physical. IOWs, to query what mappings overlap with bytes 3-14 of /dev/sda, you'd set the inputs as follows: fmh_keys[0] = { .fmr_device = major(8, 0), .fmr_physical = 3}, fmh_keys[1] = { .fmr_device = major(8, 0), .fmr_physical = 14}, Which would return you whatever is mapped in the 12 bytes starting at physical offset 3. The crash is due to insufficient range validation of keys[1] in ext4_getfsmap_datadev. On 1k-block filesystems, block 0 is not part of the filesystem, which means that s_first_data_block is nonzero. ext4_get_group_no_and_offset subtracts this quantity from the blocknr argument before cracking it into a group number and a block number within a group. IOWs, block group 0 spans blocks 1-8192 (1-based) instead of 0-8191 (0-based) like what happens with larger blocksizes. The net result of this encoding is that blocknr < s_first_data_block is not a valid input to this function. The end_fsb variable is set from the keys that are copied from userspace, which means that in the above example, its value is zero. That leads to an underflow here: blocknr = blocknr - le32_to_cpu(es->s_first_data_block); The division then operates on -1: offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >> EXT4_SB(sb)->s_cluster_bits; Leaving an impossibly large group number (2^32-1) in blocknr. ext4_getfsmap_check_keys checked that keys[0 ---truncated---
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < a70b49dc7eee5dbe3775a650ce598e3557ff5475 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < f16054ac1774915160ca4e1c73ff7a269465a1b9 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < c24f838493792b5e78a3596b4ca96375aa0af4c2 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < 1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < c5d7c31e17224d847a330180ec1b03bf390632b2 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < eb3a695aa71a514f2e7f5778e05faba3733b70a0 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < 15ebade3266b300da9cd1edce4004fe8fd6a2b88 (git)
Affected: 4a4956249dac0b9b0027949907bff0cd1a9b57fa , < c993799baf9c5861f8df91beb80e1611b12efcbd (git)
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    Linux Linux Affected: 4.13
Unaffected: 0 , < 4.13 (semver)
Unaffected: 4.14.310 , ≤ 4.14.* (semver)
Unaffected: 4.19.278 , ≤ 4.19.* (semver)
Unaffected: 5.4.237 , ≤ 5.4.* (semver)
Unaffected: 5.10.175 , ≤ 5.10.* (semver)
Unaffected: 5.15.103 , ≤ 5.15.* (semver)
Unaffected: 6.1.20 , ≤ 6.1.* (semver)
Unaffected: 6.2.7 , ≤ 6.2.* (semver)
Unaffected: 6.3 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "fs/ext4/fsmap.c"
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "5.10.175",
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              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix another off-by-one fsmap error on 1k block filesystems\n\nApparently syzbot figured out that issuing this FSMAP call:\n\nstruct fsmap_head cmd = {\n\t.fmh_count\t= ...;\n\t.fmh_keys\t= {\n\t\t{ .fmr_device = /* ext4 dev */, .fmr_physical = 0, },\n\t\t{ .fmr_device = /* ext4 dev */, .fmr_physical = 0, },\n\t},\n...\n};\nret = ioctl(fd, FS_IOC_GETFSMAP, \u0026cmd);\n\nProduces this crash if the underlying filesystem is a 1k-block ext4\nfilesystem:\n\nkernel BUG at fs/ext4/ext4.h:3331!\ninvalid opcode: 0000 [#1] PREEMPT SMP\nCPU: 3 PID: 3227965 Comm: xfs_io Tainted: G        W  O       6.2.0-rc8-achx\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014\nRIP: 0010:ext4_mb_load_buddy_gfp+0x47c/0x570 [ext4]\nRSP: 0018:ffffc90007c03998 EFLAGS: 00010246\nRAX: ffff888004978000 RBX: ffffc90007c03a20 RCX: ffff888041618000\nRDX: 0000000000000000 RSI: 00000000000005a4 RDI: ffffffffa0c99b11\nRBP: ffff888012330000 R08: ffffffffa0c2b7d0 R09: 0000000000000400\nR10: ffffc90007c03950 R11: 0000000000000000 R12: 0000000000000001\nR13: 00000000ffffffff R14: 0000000000000c40 R15: ffff88802678c398\nFS:  00007fdf2020c880(0000) GS:ffff88807e100000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 00007ffd318a5fe8 CR3: 000000007f80f001 CR4: 00000000001706e0\nCall Trace:\n \u003cTASK\u003e\n ext4_mballoc_query_range+0x4b/0x210 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80]\n ext4_getfsmap_datadev+0x713/0x890 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80]\n ext4_getfsmap+0x2b7/0x330 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80]\n ext4_ioc_getfsmap+0x153/0x2b0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80]\n __ext4_ioctl+0x2a7/0x17e0 [ext4 dfa189daddffe8fecd3cdfd00564e0f265a8ab80]\n __x64_sys_ioctl+0x82/0xa0\n do_syscall_64+0x2b/0x80\n entry_SYSCALL_64_after_hwframe+0x46/0xb0\nRIP: 0033:0x7fdf20558aff\nRSP: 002b:00007ffd318a9e30 EFLAGS: 00000246 ORIG_RAX: 0000000000000010\nRAX: ffffffffffffffda RBX: 00000000000200c0 RCX: 00007fdf20558aff\nRDX: 00007fdf1feb2010 RSI: 00000000c0c0583b RDI: 0000000000000003\nRBP: 00005625c0634be0 R08: 00005625c0634c40 R09: 0000000000000001\nR10: 0000000000000000 R11: 0000000000000246 R12: 00007fdf1feb2010\nR13: 00005625be70d994 R14: 0000000000000800 R15: 0000000000000000\n\nFor GETFSMAP calls, the caller selects a physical block device by\nwriting its block number into fsmap_head.fmh_keys[01].fmr_device.\nTo query mappings for a subrange of the device, the starting byte of the\nrange is written to fsmap_head.fmh_keys[0].fmr_physical and the last\nbyte of the range goes in fsmap_head.fmh_keys[1].fmr_physical.\n\nIOWs, to query what mappings overlap with bytes 3-14 of /dev/sda, you\u0027d\nset the inputs as follows:\n\n\tfmh_keys[0] = { .fmr_device = major(8, 0), .fmr_physical = 3},\n\tfmh_keys[1] = { .fmr_device = major(8, 0), .fmr_physical = 14},\n\nWhich would return you whatever is mapped in the 12 bytes starting at\nphysical offset 3.\n\nThe crash is due to insufficient range validation of keys[1] in\next4_getfsmap_datadev.  On 1k-block filesystems, block 0 is not part of\nthe filesystem, which means that s_first_data_block is nonzero.\next4_get_group_no_and_offset subtracts this quantity from the blocknr\nargument before cracking it into a group number and a block number\nwithin a group.  IOWs, block group 0 spans blocks 1-8192 (1-based)\ninstead of 0-8191 (0-based) like what happens with larger blocksizes.\n\nThe net result of this encoding is that blocknr \u003c s_first_data_block is\nnot a valid input to this function.  The end_fsb variable is set from\nthe keys that are copied from userspace, which means that in the above\nexample, its value is zero.  That leads to an underflow here:\n\n\tblocknr = blocknr - le32_to_cpu(es-\u003es_first_data_block);\n\nThe division then operates on -1:\n\n\toffset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) \u003e\u003e\n\t\tEXT4_SB(sb)-\u003es_cluster_bits;\n\nLeaving an impossibly large group number (2^32-1) in blocknr.\next4_getfsmap_check_keys checked that keys[0\n---truncated---"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-05-04T07:50:54.510Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a70b49dc7eee5dbe3775a650ce598e3557ff5475"
        },
        {
          "url": "https://git.kernel.org/stable/c/f16054ac1774915160ca4e1c73ff7a269465a1b9"
        },
        {
          "url": "https://git.kernel.org/stable/c/c24f838493792b5e78a3596b4ca96375aa0af4c2"
        },
        {
          "url": "https://git.kernel.org/stable/c/1d2366624b4c19a2ba6baf67fe57f4a1b0f67c05"
        },
        {
          "url": "https://git.kernel.org/stable/c/c5d7c31e17224d847a330180ec1b03bf390632b2"
        },
        {
          "url": "https://git.kernel.org/stable/c/eb3a695aa71a514f2e7f5778e05faba3733b70a0"
        },
        {
          "url": "https://git.kernel.org/stable/c/15ebade3266b300da9cd1edce4004fe8fd6a2b88"
        },
        {
          "url": "https://git.kernel.org/stable/c/c993799baf9c5861f8df91beb80e1611b12efcbd"
        }
      ],
      "title": "ext4: fix another off-by-one fsmap error on 1k block filesystems",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53143",
    "datePublished": "2025-05-02T15:56:13.656Z",
    "dateReserved": "2025-05-02T15:51:43.564Z",
    "dateUpdated": "2025-05-04T07:50:54.510Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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