{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2024-47794", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-01-09T09:49:29.737Z", "datePublished": "2025-01-11T12:25:14.419Z", "dateUpdated": "2026-08-05T11:39:59.232Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:39:59.232Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Prevent tailcall infinite loop caused by freplace\n\nThere is a potential infinite loop issue that can occur when using a\ncombination of tail calls and freplace.\n\nIn an upcoming selftest, the attach target for entry_freplace of\ntailcall_freplace.c is subprog_tc of tc_bpf2bpf.c, while the tail call in\nentry_freplace leads to entry_tc. This results in an infinite loop:\n\nentry_tc -> subprog_tc -> entry_freplace --tailcall-> entry_tc.\n\nThe problem arises because the tail_call_cnt in entry_freplace resets to\nzero each time entry_freplace is executed, causing the tail call mechanism\nto never terminate, eventually leading to a kernel panic.\n\nTo fix this issue, the solution is twofold:\n\n1. Prevent updating a program extended by an freplace program to a\n prog_array map.\n2. Prevent extending a program that is already part of a prog_array map\n with an freplace program.\n\nThis ensures that:\n\n* If a program or its subprogram has been extended by an freplace program,\n it can no longer be updated to a prog_array map.\n* If a program has been added to a prog_array map, neither it nor its\n subprograms can be extended by an freplace program.\n\nMoreover, an extension program should not be tailcalled. As such, return\n-EINVAL if the program has a type of BPF_PROG_TYPE_EXT when adding it to a\nprog_array map.\n\nAdditionally, fix a minor code style issue by replacing eight spaces with a\ntab for proper formatting." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The entire attack is built and triggered through the local `bpf(2)` syscall — two `BPF_PROG_LOAD` calls, a `BPF_LINK_CREATE` freplace attach, a `PROG_ARRAY` map update, and `BPF_PROG_TEST_RUN`. No network peer or remote input is involved, and no netdev attachment is required.\nAC:L - The attacker constructs every component of the loop (target prog, its bpf2bpf subprog, the freplace extension, and the prog_array entry) and fires it deterministically; there is no race, no memory-layout dependency, and no state outside the attacker's control. Every invocation reproduces the runaway tail-call chain.\nPR:L - Loading `BPF_PROG_TYPE_EXT` goes through `bpf_token_capable()` for CAP_BPF/CAP_NET_ADMIN/CAP_PERFMON, which grants only `ns_capable()`-level checks when a BPF token is delegated to a user namespace via bpffs `delegate_cmds`/`delegate_progs` — so a low-privileged container process with a delegated token can reach it, and no real init-namespace root is strictly needed.\nUI:N - The attacker loads, attaches, and executes the programs entirely on its own via `BPF_PROG_TEST_RUN` or by attaching the classifier and sending itself a packet. No victim action of any kind is required.\nS:U - The corruption and the crash both occur in the kernel's own stack within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - The unbounded recursion is an out-of-bounds write past the kernel stack limit with attacker-chosen BPF stack contents; on builds without CONFIG_VMAP_STACK (e.g. KASAN_GENERIC configs, where `arch/Kconfig` disables it) the overflow spills into adjacent kernel memory, yielding a corruption primitive usable for disclosing kernel data.\nI:H - Same stack overflow gives an unbounded, attacker-controlled out-of-bounds write past the stack guard limit, which on non-VMAP_STACK configurations overwrites adjacent kernel structures and is leverageable for control-flow hijack; per guidance any OOB write scores High.\nA:H - The commit states the tail-call mechanism \"never terminate[s], eventually leading to a kernel panic\" — the stack grows every cycle until it hits the guard page, producing an immediate double-fault panic (or silent corruption) within microseconds, and it can be re-triggered on every packet if the classifier is attached to a live interface." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/bpf.h", "kernel/bpf/arraymap.c", "kernel/bpf/core.c", "kernel/bpf/syscall.c", "kernel/bpf/trampoline.c" ], "versions": [ { "version": "be8704ff07d2374bcc5c675526f95e70c6459683", "lessThan": "987aa730bad3e1ef66d9f30182294daa78f6387d", "status": "affected", "versionType": "git" }, { "version": "be8704ff07d2374bcc5c675526f95e70c6459683", "lessThan": "d6083f040d5d8f8d748462c77e90547097df936e", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/linux/bpf.h", "kernel/bpf/arraymap.c", "kernel/bpf/core.c", "kernel/bpf/syscall.c", "kernel/bpf/trampoline.c" ], "versions": [ { "version": "5.6", "status": "affected" }, { "version": "0", "lessThan": "5.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.5", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "6.12.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.6", "versionEndExcluding": "6.13" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/987aa730bad3e1ef66d9f30182294daa78f6387d" }, { "url": "https://git.kernel.org/stable/c/d6083f040d5d8f8d748462c77e90547097df936e" } ], "title": "bpf: Prevent tailcall infinite loop caused by freplace", "x_generator": { "engine": "bippy-1.2.0" } } } }