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686585ec27
binfmt_flag_supported() returns 0 when the flag is supported and -1
when it is not, so every caller reads backwards:
if (binfmt_flag_supported('T'))
SKIP(return, "kernel without the 'T' flag");
Make it return a bool and flip the callers. errno from a failed probe
is still set for callers that check it.
Link: https://patch.msgid.link/20260730-work-binfmt_misc-preopen-v1-2-4a0b0da71f16@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Reviewed-by: Farid Zakaria <farid.m.zakaria@gmail.com>
96 lines
2.4 KiB
C
96 lines
2.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Test the static transparent flag 'T' of binfmt_misc. A magic-matched
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* binary is dispatched to an interpreter with the argument vector left
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* untouched, the binary passed through AT_EXECFD and mm->exe_file labeled
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* with the binary. The asserting interpreter (binfmt_transparent_interp)
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* verifies the constructed identity from inside the process and exits 0.
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*
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* Needs root for the registration; no bpf toolchain involved.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include "binfmt_misc_common.h"
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#include "kselftest_harness.h"
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#define MAGIC "#TRANSPARENT-SELFTEST#"
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#define TARGET_PATH "/tmp/binfmt_transparent_target"
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#define INTERP_PATH "/tmp/binfmt_transparent_interp"
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#define ENTRY "test_transparent"
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#define RULE(flags) ":" ENTRY ":M:0:" MAGIC "::" INTERP_PATH ":" flags
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/* The target only has to carry the magic; it is never actually loaded. */
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static int create_target(void)
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{
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char buf[128] = MAGIC "\n";
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int fd;
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unlink(TARGET_PATH);
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fd = open(TARGET_PATH, O_WRONLY | O_CREAT | O_EXCL, 0755);
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if (fd < 0)
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return -1;
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if (write(fd, buf, sizeof(buf)) != (ssize_t)sizeof(buf)) {
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close(fd);
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return -1;
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}
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close(fd);
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return 0;
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}
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FIXTURE(transparent) {
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};
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FIXTURE_SETUP(transparent)
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{
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char src[PATH_MAX];
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if (getuid() != 0)
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SKIP(return, "test must be run as root");
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if (!binfmt_misc_available())
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SKIP(return, "no binfmt_misc");
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ASSERT_EQ(artifact_path(src, sizeof(src), "binfmt_transparent_interp"), 0);
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ASSERT_EQ(copy_file(src, INTERP_PATH), 0);
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ASSERT_EQ(create_target(), 0);
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/* Skip the whole suite on a kernel that does not know 'T'. */
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if (!binfmt_flag_supported('T')) {
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ASSERT_EQ(errno, EINVAL);
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SKIP(return, "kernel without the 'T' flag");
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}
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}
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FIXTURE_TEARDOWN(transparent)
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{
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unregister(ENTRY);
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unlink(TARGET_PATH);
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unlink(INTERP_PATH);
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}
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/* Grammar sanity check: the same entry without 'T' has to register. */
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TEST_F(transparent, plain_entry_registers)
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{
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ASSERT_EQ(write_reg(RULE("")), 0);
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}
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/* 'T' preserves the whole argv, so combining it with 'P' is rejected. */
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TEST_F(transparent, rejects_preserve_argv0)
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{
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ASSERT_NE(write_reg(RULE("TP")), 0);
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EXPECT_EQ(errno, EINVAL);
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}
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/* The interpreter asserts the identity the kernel built for it. */
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TEST_F(transparent, dispatch)
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{
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ASSERT_EQ(write_reg(RULE("T")), 0);
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setenv("BINFMT_TEST_BINARY", TARGET_PATH, 1);
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setenv("BINFMT_TEST_ARGV0", PAYLOAD_ARGV0, 1);
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EXPECT_EQ(run_payload(TARGET_PATH), 0);
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}
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TEST_HARNESS_MAIN
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