From: Eduard Zingerman <eddyz87@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>, bpf@vger.kernel.org
Cc: daniel@iogearbox.net, andrii@kernel.org, memxor@gmail.com,
a.s.protopopov@gmail.com
Subject: Re: [PATCH bpf-next 01/17] bpf: Fix infinite loop in check_max_stack_depth()
Date: Wed, 23 Sep 2026 15:35:02 -0700 [thread overview]
Message-ID: <c90dc97e7ce0362564468a3604acae7b942e4623.camel@gmail.com> (raw)
In-Reply-To: <20260922011323.1298619-2-alexei.starovoitov@gmail.com>
On Tue, 2026-09-22 at 01:13 +0000, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
>
> sort_subprogs_topo() rejects recursion via direct calls, but allows cycles
> that go through ld_imm64 BPF_PSEUDO_FUNC, since the address could be taken
> for an async callback. The main verifier pass limits the number of frames,
> but it doesn't follow calls into global functions.
> So the following program passes both:
>
> static int cb(u32 i, void *ctx) { return foo(i); }
> static int foo(int x) { return bar(x); }
> int bar(int x) { bpf_loop(1, cb, NULL, 0); return 0; }
>
> SEC("socket") int prog(void *ctx) { return cb(0, NULL); }
>
> cb -> foo -> bar -> bpf_loop -> cb is unbounded recursion.
> check_max_stack_depth_subprog() walks this cycle too. None of
> the functions use stack and the frame counter is reset by every global
> function, so neither stack size nor frame limit is hit and bpf_prog_load()
> spins forever.
>
> Reject a call into a subprog that is already in the chain of callers.
> Async callbacks are skipped earlier and are not affected.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
...
next prev parent reply other threads:[~2026-09-23 22:35 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 1:13 [PATCH bpf-next 00/17] bpf: Indirect calls of bpf subprogs (callx) Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 01/17] bpf: Fix infinite loop in check_max_stack_depth() Alexei Starovoitov
2026-09-22 2:01 ` bot+bpf-ci
2026-09-22 2:56 ` Alexei Starovoitov
2026-09-23 22:35 ` Eduard Zingerman [this message]
2026-09-22 1:13 ` [PATCH bpf-next 02/17] selftests/bpf: Test recursion through a global function and a callback Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 03/17] bpf: Don't fold loads from insn_array maps into constants Alexei Starovoitov
2026-09-23 22:39 ` Eduard Zingerman
2026-09-23 23:12 ` Alexei Starovoitov
2026-09-24 0:19 ` bot+bpf-ci
2026-09-22 1:13 ` [PATCH bpf-next 04/17] bpf: Prepare static analysis passes for callx instruction Alexei Starovoitov
2026-09-23 23:10 ` Eduard Zingerman
2026-09-23 23:51 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 05/17] bpf: Add callx instruction to call bpf subprogs indirectly Alexei Starovoitov
2026-09-24 0:09 ` Eduard Zingerman
2026-09-22 1:13 ` [PATCH bpf-next 06/17] bpf: Add callx calls to the call graph Alexei Starovoitov
2026-09-22 1:27 ` sashiko-bot
2026-09-22 2:54 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 07/17] bpf, x86: Add JIT support for callx Alexei Starovoitov
2026-09-22 1:27 ` sashiko-bot
2026-09-22 2:53 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 08/17] bpf, arm64: " Alexei Starovoitov
2026-09-22 15:05 ` Puranjay Mohan
2026-09-22 1:13 ` [PATCH bpf-next 09/17] bpf: Discover subprogs described by func_info Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 10/17] bpf: Recognize pointers to functions in read-only maps Alexei Starovoitov
2026-09-22 1:31 ` sashiko-bot
2026-09-22 3:01 ` Alexei Starovoitov
2026-09-24 0:46 ` bot+bpf-ci
2026-09-24 2:12 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 11/17] libbpf: Support pointers to static functions in data when linking Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 12/17] libbpf: Resolve pointers to functions in read-only data Alexei Starovoitov
2026-09-24 0:33 ` bot+bpf-ci
2026-09-24 2:13 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 13/17] libbpf: Treat .data.rel.ro as " Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 14/17] libbpf: Support pointers to functions in read-only data in light skeleton Alexei Starovoitov
2026-09-22 2:01 ` bot+bpf-ci
2026-09-22 2:55 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 15/17] selftests/bpf: Add tests for callx Alexei Starovoitov
2026-09-24 0:33 ` bot+bpf-ci
2026-09-24 2:13 ` Alexei Starovoitov
2026-09-22 1:13 ` [PATCH bpf-next 16/17] selftests/bpf: Add tests for callx through pointers in read-only data Alexei Starovoitov
2026-09-22 2:01 ` bot+bpf-ci
2026-09-24 0:33 ` bot+bpf-ci
2026-09-22 1:13 ` [PATCH bpf-next 17/17] bpf, docs: Document callx instruction Alexei Starovoitov
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