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From: Dave Marchevsky <davemarchevsky@fb.com>
To: <bpf@vger.kernel.org>
Cc: <kernel-team@fb.com>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
	Dave Marchevsky <davemarchevsky@fb.com>
Subject: [PATCH bpf-next v2 1/3] bpf: refine retval for bpf_get_task_stack helper
Date: Fri, 16 Apr 2021 13:47:02 -0700	[thread overview]
Message-ID: <20210416204704.2816874-2-davemarchevsky@fb.com> (raw)
In-Reply-To: <20210416204704.2816874-1-davemarchevsky@fb.com>

Verifier can constrain the min/max bounds of bpf_get_task_stack's return
value more tightly than the default tnum_unknown. Like bpf_get_stack,
return value is num bytes written into a caller-supplied buf, or error,
so do_refine_retval_range will work.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 852541a435ef..348e97f77003 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5767,6 +5767,7 @@ static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
 
 	if (ret_type != RET_INTEGER ||
 	    (func_id != BPF_FUNC_get_stack &&
+	     func_id != BPF_FUNC_get_task_stack &&
 	     func_id != BPF_FUNC_probe_read_str &&
 	     func_id != BPF_FUNC_probe_read_kernel_str &&
 	     func_id != BPF_FUNC_probe_read_user_str))
-- 
2.30.2


  reply	other threads:[~2021-04-16 20:47 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 20:47 [PATCH bpf-next v2 0/3] bpf: refine retval for bpf_get_task_stack helper Dave Marchevsky
2021-04-16 20:47 ` Dave Marchevsky [this message]
2021-04-16 20:47 ` [PATCH bpf-next v2 2/3] bpf/selftests: add bpf_get_task_stack retval bounds verifier test Dave Marchevsky
2021-04-16 20:47 ` [PATCH bpf-next v2 3/3] bpf/selftests: add bpf_get_task_stack retval bounds test_prog Dave Marchevsky
2021-04-20  2:20 ` [PATCH bpf-next v2 0/3] bpf: refine retval for bpf_get_task_stack helper Alexei Starovoitov

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