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bpf: Mark signal tracepoint siginfo arguments as scalar

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The signal_generate and signal_deliver tracepoints declare their info
argument as a struct kernel_siginfo pointer. btf_ctx_access() therefore
treats it as a trusted pointer for tp_btf programs.

Signal delivery also uses SEND_SIG_NOINFO and SEND_SIG_PRIV as special
values for this argument. Those values are zero and one respectively,
and are not pointers. A tp_btf program can currently dereference either
value and fault the kernel. In particular, signal_generate can run from
timer interrupt context, turning the fault into a kernel panic.

Record both tracepoints in raw_tp_null_args[] and mark argument one as
a non-pointer. This preserves scalar access to the cookie while rejecting
direct and helper-mediated pointer use. Merely marking it nullable would
not suffice because SEND_SIG_PRIV is nonzero.

Fixes: 838a10bd2e ("bpf: Augment raw_tp arguments with PTR_MAYBE_NULL")
Reported-by: Nicholas Carlini <npc@anthropic.com>
Suggested-by: Nicholas Carlini <npc@anthropic.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260903144433.1716731-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kumar Kartikeya Dwivedi 2026-09-03 16:44:19 +02:00 committed by Alexei Starovoitov
parent 1329a7aa33
commit 77515ab12e
1 changed files with 3 additions and 0 deletions
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kernel/bpf/btf.c
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@ -6732,6 +6732,9 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = {
{ "rxrpc_resend", 0x10 },
{ "rxrpc_tq", 0x10 },
{ "rxrpc_client", 0x1 },
/* signal */
{ "signal_generate", 0x20 },
{ "signal_deliver", 0x20 },
/* skb */
{"kfree_skb", 0x1000},
/* sunrpc */