7e428638bd
Somehow recently I frequently hit the following test failure with either ./test_progs or ./test_progs-cpuv4: serial_test_ptr_untrusted:PASS:skel_open 0 nsec serial_test_ptr_untrusted:PASS:lsm_attach 0 nsec serial_test_ptr_untrusted:PASS:raw_tp_attach 0 nsec serial_test_ptr_untrusted:FAIL:cmp_tp_name unexpected cmp_tp_name: actual -115 != expected 0 #182 ptr_untrusted:FAIL Further investigation found the failure is due to bpf_probe_read_user_str() where reading user-level string attr->raw_tracepoint.name is not successfully, most likely due to the string itself still in disk and not populated into memory yet. One solution is do a printf() call of the string before doing bpf syscall which will force the raw_tracepoint.name into memory. But I think a more robust solution is to use bpf_copy_from_user() which is used in sleepable program and can tolerate page fault, and the fix here used the latter approach. Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20240204194452.2785936-1-yonghong.song@linux.dev
29 lines
548 B
C
29 lines
548 B
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
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#include "vmlinux.h"
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#include <bpf/bpf_tracing.h>
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char tp_name[128];
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SEC("lsm.s/bpf")
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int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
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{
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switch (cmd) {
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case BPF_RAW_TRACEPOINT_OPEN:
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bpf_copy_from_user(tp_name, sizeof(tp_name) - 1,
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(void *)attr->raw_tracepoint.name);
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break;
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default:
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break;
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}
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return 0;
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}
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SEC("raw_tracepoint")
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int BPF_PROG(raw_tp_run)
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{
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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