In the Linux kernel, the following vulnerability has been resolved:
bpf: consider that tail calls invalidate packet pointers
Tail-called programs could execute any of the helpers that invalidate
packet pointers. Hence, conservatively assume that each tail call
invalidates packet pointers.
Making the change in bpf_helper_changes_pkt_data() automatically makes
use of check_cfg() logic that computes 'changes_pkt_data' effect for
global sub-programs, such that the following program could be
rejected:
    int tail_call(struct __sk_buff *sk)
    {
    	bpf_tail_call_static(sk, &jmp_table, 0);
    	return 0;
    }
    SEC("tc")
    int not_safe(struct __sk_buff *sk)
    {
    	int *p = (void *)(long)sk->data;
    	... make p valid ...
    	tail_call(sk);
    	*p = 42; /* this is unsafe */
    	...
    }
The tc_bpf2bpf.c:subprog_tc() needs change: mark it as a function that
can invalidate packet pointers. Otherwise, it can't be freplaced with
tailcall_freplace.c:entry_freplace() that does a tail call.
                
            Metrics
Affected Vendors & Products
References
        History
                    Sat, 12 Jul 2025 13:45:00 +0000
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Tue, 06 May 2025 14:30:00 +0000
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Mon, 05 May 2025 15:00:00 +0000
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| Description | In the Linux kernel, the following vulnerability has been resolved: bpf: consider that tail calls invalidate packet pointers Tail-called programs could execute any of the helpers that invalidate packet pointers. Hence, conservatively assume that each tail call invalidates packet pointers. Making the change in bpf_helper_changes_pkt_data() automatically makes use of check_cfg() logic that computes 'changes_pkt_data' effect for global sub-programs, such that the following program could be rejected: int tail_call(struct __sk_buff *sk) { bpf_tail_call_static(sk, &jmp_table, 0); return 0; } SEC("tc") int not_safe(struct __sk_buff *sk) { int *p = (void *)(long)sk->data; ... make p valid ... tail_call(sk); *p = 42; /* this is unsafe */ ... } The tc_bpf2bpf.c:subprog_tc() needs change: mark it as a function that can invalidate packet pointers. Otherwise, it can't be freplaced with tailcall_freplace.c:entry_freplace() that does a tail call. | |
| Title | bpf: consider that tail calls invalidate packet pointers | |
| References |  | 
 MITRE
                        MITRE
                    Status: PUBLISHED
Assigner: Linux
Published: 2025-05-05T14:53:34.153Z
Updated: 2025-05-09T08:06:10.185Z
Reserved: 2025-04-16T07:19:43.804Z
Link: CVE-2024-58237
 Vulnrichment
                        Vulnrichment
                    No data.
 NVD
                        NVD
                    Status : Awaiting Analysis
Published: 2025-05-05T15:15:54.010
Modified: 2025-05-09T08:15:19.030
Link: CVE-2024-58237
 Redhat
                        Redhat