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id = 1687
title = "Memory leak for x86 guest on macOS ARM host"
state = "opened"
created_at = "2023-06-05T19:27:51.499Z"
closed_at = "n/a"
labels = []
url = "https://gitlab.com/qemu-project/qemu/-/issues/1687"
host-os = "macOS Darwin"
host-arch = "ARM"
qemu-version = "n/a"
guest-os = "Ubuntu 22.04"
guest-arch = "x86"
description = """QEMU is used by docker to run `x86` binaries on Apple silicon. Then using `mmap` followed by `munmap` results in a memory leak manifested by continuously growing RSS memory usage when running `mmap` and `munmap` in a loop, e.g., when running the following binary:
```
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
const int page = 4096;
int work(int N) {
int *ptr = mmap(NULL, N * sizeof(int), PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
if (ptr == MAP_FAILED) {
printf("Mapping Failed\\n");
return 1;
}
for(int i = 0; i < N; i++) {
ptr[i] = i * 10;
}
int err = munmap(ptr, N * sizeof(int));
if (err != 0) {
printf("UnMapping Failed\\n");
return 1;
}
return 0;
}
int main() {
int N = page * 1024;
while (1) {
int res = work(N);
if (res) {
return res;
}
printf(".\\n");
}
return 0;
}
```"""
reproduce = """```
$ LEAK=$(docker run --platform linux/amd64 -d -it martin2718/mmap-leak ./a.out)
$ docker exec -it $LEAK top # you should observe that RES for a.out keeps growing
$ docker exec -it $LEAK pmap -x 1 # you should see a single memory mapping whose RSS memory usage keeps growing
$ docker kill $LEAK # abort the experiment
```"""
additional = "n/a"
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