WSL: ftruncate does not truncate mmap'd files #902
Description
Please use the following bug reporting template to help produce actionable and reproducible issues:
- A brief description
ftruncate does not truncate mmap'd files while they are mmap'd. - Expected results
file gets truncated to desired size in bytes, even when mmap'd; SIGBUS occurs if memory outside new file bounds is accessed. (This is the behavior on Ubuntu.) - Actual results (with terminal output if applicable)
file does not get truncated - Your Windows build number
14393 - Steps / commands required to reproduce the error
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#define FAIL exit(errno);
int main() {
/* prepare test data */
int buf_size = 8102;
char* buf = malloc(buf_size);
if(NULL == buf) {
FAIL
}
memset(buf, '?', buf_size);
int fd = open("test_buffer", O_RDWR | O_CREAT);
if(fd < 0) {
FAIL
}
/* run test */
write(fd, buf, buf_size);
char* mm = mmap(NULL, buf_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if(MAP_FAILED == mm) {
FAIL
}
memset(mm, '!', buf_size);
int tres = ftruncate(fd, 16);
if(0 != tres) { /* okay, trying again later */
write(STDOUT_FILENO, "NOFIRST\n", 9);
errno = 0;
}
int mures = munmap(mm, buf_size);
if(0 != mures) {
FAIL
}
tres = ftruncate(fd, 16);
if(0 != tres) {
write(STDOUT_FILENO, "FAIL BOTH\n", 11);
exit(1);
}
write(STDOUT_FILENO, "SUCCESS\n", 9);
close(fd);
}
- Strace of the failing command
`execve("./min_test.bin", ["./min_test.bin"], [/* 23 vars */]) = 0
brk(0) = 0x12ab000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c97540000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=64852, ...}) = 0
mmap(NULL, 64852, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7c97530000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P \2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1840928, ...}) = 0
mmap(NULL, 3949248, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f7c96e30000
mprotect(0x7f7c96fea000, 2097152, PROT_NONE) = 0
mmap(0x7f7c971ea000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ba000) = 0x7f7c971ea000
mmap(0x7f7c971f0000, 17088, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f7c971f0000
close(3) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c97520000
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7c97510000
arch_prctl(ARCH_SET_FS, 0x7f7c97510740) = 0
mprotect(0x7f7c971ea000, 16384, PROT_READ) = 0
mprotect(0x600000, 4096, PROT_READ) = 0
mprotect(0x7f7c97422000, 4096, PROT_READ) = 0
munmap(0x7f7c97530000, 64852) = 0
brk(0) = 0x12ab000
brk(0x12cd000) = 0x12cd000
open("test_buffer", O_RDWR|O_CREAT, 0112547600) = 3
write(3, "????????????????????????????????"..., 8102) = 8102
mmap(NULL, 8102, PROT_READ|PROT_WRITE, MAP_SHARED, 3, 0) = 0x7f7c9754b000
ftruncate(3, 16) = -1 EINVAL (Invalid argument)
write(1, "NOFIRST\n\0", 9) = 9
munmap(0x7f7c9754b000, 8102) = 0
ftruncate(3, 16) = 0
write(1, "SUCCESS\n\0", 9) = 9
close(3) = 0
exit_group(0) = ?
+++ exited with 0 +++
- Required packages and commands to install
apt-get -y install build-essential
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