pkg/csource: setup sysctl's in C reproducers

Sysctl's are not captured as part of reproducers.
This can result in failure to reproduce a bug on developer machine.
Include sysctl setup as part of C reproducers.

1 files changed, 40 insertions, 0 deletions

diff --git a/executor/common_linux.h b/executor/common_linux.h
index 1d372af7f..11ce0a6e9 100644
--- a/executor/common_linux.h
+++ b/executor/common_linux.h
@@ -4578,6 +4578,46 @@ static void setup_usb()
 }
 #endif
 
+#if SYZ_EXECUTOR || SYZ_SYSCTL
+static void setup_sysctl()
+{
+	static struct {
+		const char* name;
+		const char* data;
+	} files[] = {
+	    // nmi_check_duration() prints "INFO: NMI handler took too long" on slow debug kernels.
+	    // It happens a lot in qemu, and the messages are frequently corrupted
+	    // (intermixed with other kernel output as they are printed from NMI)
+	    // and are not matched against the suppression in pkg/report.
+	    // This write prevents these messages from being printed.
+	    {"/sys/kernel/debug/x86/nmi_longest_ns", "10000000000"},
+	    // This is part of deterministic hang/stall detection.
+	    // Don't change this without considering workqueue.watchdog_thresh,
+	    // CONFIG_RCU_CPU_STALL_TIMEOUT and CONFIG_DEFAULT_HUNG_TASK_TIMEOUT.
+	    {"/proc/sys/kernel/watchdog_thresh", "55"},
+	    {"/proc/sys/kernel/hung_task_check_interval_secs", "20"},
+	    // This gives more interesting coverage.
+	    {"/proc/sys/net/core/bpf_jit_enable", "1"},
+	    // bpf_jit_kallsyms and disabling bpf_jit_harden are required
+	    // for unwinding through bpf functions.
+	    {"/proc/sys/net/core/bpf_jit_kallsyms", "1"},
+	    {"/proc/sys/net/core/bpf_jit_harden", "0"},
+	    // This is to provide more useful info in crash reports.
+	    {"/proc/sys/kernel/kptr_restrict", "0"},
+	    {"/proc/sys/kernel/softlockup_all_cpu_backtrace", "1"},
+	    // This is to restrict effects of recursive exponential mounts, for details see
+	    // "mnt: Add a per mount namespace limit on the number of mounts" commit.
+	    {"/proc/sys/fs/mount-max", "100"},
+	    // Dumping all tasks to console can take too long.
+	    {"/proc/sys/vm/oom_dump_tasks", "0"},
+	};
+	for (size_t i = 0; i < sizeof(files) / sizeof(files[0]); i++) {
+		if (!write_file(files[i].name, files[i].data))
+			printf("write to %s failed: %s\n", files[i].name, strerror(errno));
+	}
+}
+#endif
+
 #if GOARCH_s390x
 #include <sys/mman.h>
 // Ugly way to work around gcc's "error: function called through a non-compatible type".