NODERAWFS: utime, utimensat set wrong atime and mtime (overflow issue?)

[tiran]

The utimensat function of NODERAWFS sets wrong atime and mtime. The issue looks like an overflow problem to me.

Update 1 It's a factor 1000 issue.

Update 2 The utimensat handler is also missing a check for times == NULL. Value 0 indicates that the OS should set mtime and atime to current time (NOW).

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.7 (48a16209b1a0de5efd8112ce6430415730008d18)
clang version 15.0.0 (https://github.com/llvm/llvm-project fbce4a78035c32792b0a13cf1f169048b822c06b)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /emsdk/upstream/bin

Reproducer

#include <fcntl.h>
#include <sys/stat.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define PATH "utime.test"
#define TS 1646823705

int main(void) {
    int fd = open(PATH, O_RDWR | O_CREAT, 0644);
    close(fd);

    struct timespec times[2];
    times[0].tv_sec = TS;
    times[0].tv_nsec = 0;
    times[1].tv_sec = times[0].tv_sec;
    times[1].tv_nsec = times[0].tv_nsec;
    
    utimensat(AT_FDCWD, PATH, times, 0);

    struct stat st;
    stat(PATH, &st);
    fprintf(stdout, "mtime: %li, atime: %li\n", st.st_mtime, st.st_atime);
    return 0;
}

$ gcc -outime utime.c && ./utime && stat utime.test 
mtime: 1646823705, atime: 1646823705
  File: utime.test
  Size: 0               Blocks: 0          IO Block: 4096   regular empty file
Device: fd03h/64771d    Inode: 8942735     Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2022-03-09 11:01:45.000000000 +0000
Modify: 2022-03-09 11:01:45.000000000 +0000
Change: 2022-03-09 11:17:03.726773876 +0000
 Birth: -

$ emcc -s NODERAWFS -o utime.js utime.c && node utime.js && stat utime.test
mtime: 2147483647, atime: 2147483647
  File: utime.test
  Size: 0               Blocks: 0          IO Block: 4096   regular empty file
Device: fd03h/64771d    Inode: 8942735     Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2446-05-10 22:38:55.000000000 +0000
Modify: 2446-05-10 22:38:55.000000000 +0000
Change: 2022-03-09 11:17:35.650125660 +0000
 Birth: -

Please note the difference between stat() call and stat command output. The stat command returns year 2446. The timestamp 2147483647 is the beginning of the epochalypse. It appears that Emscripten NODERAWFS is not 2038-safe yet, but that is a different issue.

[tiran]

utime is also affected:

    struct utimbuf times = {TS, TS};
    utime(PATH, &times);

[tiran]

The value is off by factor 1000. Node's FS layer accepts times in seconds, not milliseconds, https://nodejs.org/api/fs.html#filehandleutimesatime-mtime

This should do the trick:

--- a/src/library_syscall.js
+++ b/src/library_syscall.js
@@ -1048,11 +1048,11 @@ var SyscallsLibrary = {
     path = SYSCALLS.calculateAt(dirfd, path, true);
     var seconds = {{{ makeGetValue('times', C_STRUCTS.timespec.tv_sec, 'i32') }}};
     var nanoseconds = {{{ makeGetValue('times', C_STRUCTS.timespec.tv_nsec, 'i32') }}};
-    var atime = (seconds*1000) + (nanoseconds/(1000*1000));
+    var atime = seconds + (nanoseconds/(1000*1000*1000));
     times += {{{ C_STRUCTS.timespec.__size__ }}};
     seconds = {{{ makeGetValue('times', C_STRUCTS.timespec.tv_sec, 'i32') }}};
     nanoseconds = {{{ makeGetValue('times', C_STRUCTS.timespec.tv_nsec, 'i32') }}};
-    var mtime = (seconds*1000) + (nanoseconds/(1000*1000));
+    var mtime = seconds + (nanoseconds/(1000*1000*1000));
     FS.utime(path, atime, mtime);
     return 0;
   },

[sbc100]

Thanks for the report and for the fix. Would you like to submit at PR? (No worries if there is some reason why can't/don't want to, just curious).

[tiran]

Thanks for the report and for the fix. Would you like to submit at PR? (No worries if there is some reason why can't/don't want to, just curious).

I have not figured out how to solve the second problem with utimensat. It does not handle the special case times == NULL.