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Handle AT_SYMLINK_NOFOLLOW in __syscall_faccessat #26500

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Handle AT_SYMLINK_NOFOLLOW in __syscall_faccessat #26500

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5 changes: 3 additions & 2 deletions src/lib/libsyscall.js
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Original file line number Diff line number Diff line change
Expand Up @@ -930,14 +930,15 @@ var SyscallsLibrary = {
__syscall_faccessat: (dirfd, path, amode, flags) => {
path = SYSCALLS.getStr(path);
#if ASSERTIONS
assert(!flags || flags == {{{ cDefs.AT_EACCESS }}});
assert(!(flags & ~({{{ cDefs.AT_EACCESS }}} | {{{ cDefs.AT_SYMLINK_NOFOLLOW }}})));
#endif
path = SYSCALLS.calculateAt(dirfd, path);
if (amode & ~{{{ cDefs.S_IRWXO }}}) {
// need a valid mode
return -{{{ cDefs.EINVAL }}};
}
var lookup = FS.lookupPath(path, { follow: true });
var nofollow = !!(flags & {{{ cDefs.AT_SYMLINK_NOFOLLOW }}});
var lookup = FS.lookupPath(path, { follow: !nofollow });
var node = lookup.node;
if (!node) {
return -{{{ cDefs.ENOENT }}};
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22 changes: 22 additions & 0 deletions test/unistd/access.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,27 @@ void test_lchmod() {
#endif
}

void test_symlink_nofollow() {
#if defined(MEMFS)
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@sbc100 sbc100 Mar 23, 2026

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Is this because windows does not support symlinks?

I wonder if this would be controlled instead via a separate "-DNO_SYMLINKS" compile flag that we set if and only if we are running on windows and using rawfs?

FILE* f = fopen("target_file", "w");
fclose(f);
symlink("target_file", "test_symlink");
symlink("dangling_target", "dangling_symlink");

// With AT_SYMLINK_NOFOLLOW, faccessat checks the symlink itself, not the target
assert(faccessat(AT_FDCWD, "test_symlink", F_OK, AT_SYMLINK_NOFOLLOW) == 0);

// Dangling symlink should still be found with AT_SYMLINK_NOFOLLOW (symlink exists)
assert(faccessat(AT_FDCWD, "dangling_symlink", F_OK, AT_SYMLINK_NOFOLLOW) == 0);

// Without AT_SYMLINK_NOFOLLOW, dangling symlink should fail
assert(faccessat(AT_FDCWD, "dangling_symlink", F_OK, 0) != 0);

// Combined flags should work
assert(faccessat(AT_FDCWD, "test_symlink", F_OK, AT_EACCESS | AT_SYMLINK_NOFOLLOW) == 0);
#endif
}

void test_chmod_errors() {
EM_ASM(
var ex;
Expand Down Expand Up @@ -119,6 +140,7 @@ int main() {
test_rename();
test_fchmod();
test_lchmod();
test_symlink_nofollow();
test_chmod_errors();

return 0;
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