In the Linux kernel, the following vulnerability has been resolved:
ipmr: do not call mrmfcuses_dev() for unres entries
syzbot found that calling mrmfcusesdev() for unres entries would crash [1], because c->mfcun.res.minvif / c->mfcun.res.maxvif alias to "struct skbuff_head unresolved", which contain two pointers.
This code never worked, lets remove it.
[1] Unable to handle kernel paging request at virtual address ffff5fff2d536613 KASAN: maybe wild-memory-access in range [0xfffefff96a9b3098-0xfffefff96a9b309f] Modules linked in: CPU: 1 UID: 0 PID: 7321 Comm: syz.0.16 Not tainted 6.13.0-rc7-syzkaller-g1950a0af2d55 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : mrmfcusesdev net/ipv4/ipmrbase.c:290 [inline] pc : mrtabledump+0x5a4/0x8b0 net/ipv4/ipmrbase.c:334 lr : mrmfcusesdev net/ipv4/ipmrbase.c:289 [inline] lr : mrtabledump+0x694/0x8b0 net/ipv4/ipmrbase.c:334 Call trace: mrmfcusesdev net/ipv4/ipmrbase.c:290 [inline] (P) mrtabledump+0x5a4/0x8b0 net/ipv4/ipmrbase.c:334 (P) mrrtmdumproute+0x254/0x454 net/ipv4/ipmrbase.c:382 ipmrrtmdumproute+0x248/0x4b4 net/ipv4/ipmr.c:2648 rtnldumpall+0x2e4/0x4e8 net/core/rtnetlink.c:4327 rtnldumpit+0x98/0x1d0 net/core/rtnetlink.c:6791 netlinkdump+0x4f0/0xbc0 net/netlink/afnetlink.c:2317 netlinkrecvmsg+0x56c/0xe64 net/netlink/afnetlink.c:1973 sockrecvmsgnosec net/socket.c:1033 [inline] sockrecvmsg net/socket.c:1055 [inline] sockreaditer+0x2d8/0x40c net/socket.c:1125 newsyncread fs/readwrite.c:484 [inline] vfsread+0x740/0x970 fs/readwrite.c:565 ksysread+0x15c/0x26c fs/read_write.c:708
[
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-00d711bd",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@26bb7d991f04eeef47dfad23e533834995c26f7a",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-01f644ce",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@57177c5f47a8da852f8d76cf6945cf803f8bb9e5",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-275d4183",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@15a901361ec3fb1c393f91880e1cbf24ec0a88bd",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-298643dc",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@547ef7e8cbb98f966c8719a3e15d4e078aaa9b47",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-29ad2d83",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@53df27fd38f84bd3cd6b004eb4ff3c4903114f1d",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-2ee66e8f",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@a099834a51ccf9bbba3de86a251b3433539abfde",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-58bfd811",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@71a0fcb68c0a5f3ec912b540cd5d72148e6ee5f1",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-71dc2ab7",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@b379b3162ff55a70464c6a934ae9bf0497478a62",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-864e77c5",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@53df27fd38f84bd3cd6b004eb4ff3c4903114f1d",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-88fafe0b",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@57177c5f47a8da852f8d76cf6945cf803f8bb9e5",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-97618041",
        "signature_type": "Line",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "95025872401984315686136960694973677947",
                "144725881363960847039053380178697742909",
                "21253729950462716669578535424716041300",
                "127955016205442905397342620081094800166",
                "323257112210912362546552360189890496357",
                "12284271378390446216366004124671835023"
            ]
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@b379b3162ff55a70464c6a934ae9bf0497478a62",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-d2e27beb",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@547ef7e8cbb98f966c8719a3e15d4e078aaa9b47",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-d721aa70",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@15a901361ec3fb1c393f91880e1cbf24ec0a88bd",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-ede79106",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@a099834a51ccf9bbba3de86a251b3433539abfde",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-ee634d78",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@71a0fcb68c0a5f3ec912b540cd5d72148e6ee5f1",
        "deprecated": false
    },
    {
        "signature_version": "v1",
        "id": "CVE-2025-21719-fe294653",
        "signature_type": "Function",
        "digest": {
            "length": 1258.0,
            "function_hash": "187148401677273273615111087115486109936"
        },
        "target": {
            "file": "net/ipv4/ipmr_base.c",
            "function": "mr_table_dump"
        },
        "source": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git@26bb7d991f04eeef47dfad23e533834995c26f7a",
        "deprecated": false
    }
]