ghsa-mqrj-rhjj-jp5m
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
bpf: track changes_pkt_data property for global functions
When processing calls to certain helpers, verifier invalidates all packet pointers in a current state. For example, consider the following program:
__attribute__((__noinline__))
long skb_pull_data(struct __sk_buff *sk, __u32 len)
{
return bpf_skb_pull_data(sk, len);
}
SEC("tc")
int test_invalidate_checks(struct __sk_buff *sk)
{
int *p = (void *)(long)sk->data;
if ((void *)(p + 1) > (void *)(long)sk->data_end) return TCX_DROP;
skb_pull_data(sk, 0);
*p = 42;
return TCX_PASS;
}
After a call to bpf_skb_pull_data() the pointer 'p' can't be used safely. See function filter.c:bpf_helper_changes_pkt_data() for a list of such helpers.
At the moment verifier invalidates packet pointers when processing helper function calls, and does not traverse global sub-programs when processing calls to global sub-programs. This means that calls to helpers done from global sub-programs do not invalidate pointers in the caller state. E.g. the program above is unsafe, but is not rejected by verifier.
This commit fixes the omission by computing field bpf_subprog_info->changes_pkt_data for each sub-program before main verification pass. changes_pkt_data should be set if: - subprogram calls helper for which bpf_helper_changes_pkt_data returns true; - subprogram calls a global function, for which bpf_subprog_info->changes_pkt_data should be set.
The verifier.c:check_cfg() pass is modified to compute this information. The commit relies on depth first instruction traversal done by check_cfg() and absence of recursive function calls: - check_cfg() would eventually visit every call to subprogram S in a state when S is fully explored; - when S is fully explored: - every direct helper call within S is explored (and thus changes_pkt_data is set if needed); - every call to subprogram S1 called by S was visited with S1 fully explored (and thus S inherits changes_pkt_data from S1).
The downside of such approach is that dead code elimination is not taken into account: if a helper call inside global function is dead because of current configuration, verifier would conservatively assume that the call occurs for the purpose of the changes_pkt_data computation.
{
"affected": [],
"aliases": [
"CVE-2024-58098"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-05-05T15:15:53Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: track changes_pkt_data property for global functions\n\nWhen processing calls to certain helpers, verifier invalidates all\npacket pointers in a current state. For example, consider the\nfollowing program:\n\n __attribute__((__noinline__))\n long skb_pull_data(struct __sk_buff *sk, __u32 len)\n {\n return bpf_skb_pull_data(sk, len);\n }\n\n SEC(\"tc\")\n int test_invalidate_checks(struct __sk_buff *sk)\n {\n int *p = (void *)(long)sk-\u003edata;\n if ((void *)(p + 1) \u003e (void *)(long)sk-\u003edata_end) return TCX_DROP;\n skb_pull_data(sk, 0);\n *p = 42;\n return TCX_PASS;\n }\n\nAfter a call to bpf_skb_pull_data() the pointer \u0027p\u0027 can\u0027t be used\nsafely. See function filter.c:bpf_helper_changes_pkt_data() for a list\nof such helpers.\n\nAt the moment verifier invalidates packet pointers when processing\nhelper function calls, and does not traverse global sub-programs when\nprocessing calls to global sub-programs. This means that calls to\nhelpers done from global sub-programs do not invalidate pointers in\nthe caller state. E.g. the program above is unsafe, but is not\nrejected by verifier.\n\nThis commit fixes the omission by computing field\nbpf_subprog_info-\u003echanges_pkt_data for each sub-program before main\nverification pass.\nchanges_pkt_data should be set if:\n- subprogram calls helper for which bpf_helper_changes_pkt_data\n returns true;\n- subprogram calls a global function,\n for which bpf_subprog_info-\u003echanges_pkt_data should be set.\n\nThe verifier.c:check_cfg() pass is modified to compute this\ninformation. The commit relies on depth first instruction traversal\ndone by check_cfg() and absence of recursive function calls:\n- check_cfg() would eventually visit every call to subprogram S in a\n state when S is fully explored;\n- when S is fully explored:\n - every direct helper call within S is explored\n (and thus changes_pkt_data is set if needed);\n - every call to subprogram S1 called by S was visited with S1 fully\n explored (and thus S inherits changes_pkt_data from S1).\n\nThe downside of such approach is that dead code elimination is not\ntaken into account: if a helper call inside global function is dead\nbecause of current configuration, verifier would conservatively assume\nthat the call occurs for the purpose of the changes_pkt_data\ncomputation.",
"id": "GHSA-mqrj-rhjj-jp5m",
"modified": "2025-05-05T15:30:53Z",
"published": "2025-05-05T15:30:53Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-58098"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1d572c60488b52882b719ed273767ee3b280413d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/51081a3f25c742da5a659d7fc6fd77ebfdd555be"
}
],
"schema_version": "1.4.0",
"severity": []
}
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.