tar honor umask test fails on Android

[kongy]

When integrating e4a106afa0e93e04c5c73c422fe615c6f7bd96f0 to Android, the newly introduced tar honor umask test fails:

FAIL: tar honor umask
echo -ne '' | umask 0022 && rm -rf dir && mkdir dir && tar xf $FILES/tar/dir.tar && stat -c%A dir dir/file
--- expected    2024-07-23 15:26:31.080000408 +0000
+++ actual  2024-07-23 15:26:31.196000408 +0000
@@ -1,2 +1,2 @@
-drwxr-xr-x
--rwxr-xr-x
+drwxrwxrwx
+-rwxrwxrwx

[enh-google]

fwiw, it's only that test that fails (the two following ones are fine).

one oddity worth mentioning is that the default umask for root on Android is 0?

[enh-google]

strace on the host, where the test passes:

openat(AT_FDCWD, "dir/file", O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0700) = 4
copy_file_range(3, NULL, 4, NULL, 6, 0) = 6
close(4)                                = 0
geteuid()                               = 73769 
chmod("dir/file", 0755)                 = 0

strace on Android, where it fails:

openat(AT_FDCWD, "dir/file", O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0700) = 4
copy_file_range(3, NULL, 4, NULL, 6, 0) = 6
close(4)                                = 0
geteuid()                               = 0
fchownat(AT_FDCWD, "dir/file", 1000, 1000, AT_SYMLINK_NOFOLLOW) = 0 
fchmodat(AT_FDCWD, "dir/file", 0100777) = 0

[enh-google]

so a bit more printf() debugging, and it looks like in

  if (!S_ISLNK(ala)) chmod(name, FLAG(p) ? ala : ala&0777&~toys.old_umask);

Android always has FLAG(p) set?

which looks like it's probably coming from tar_main()?

  if (!geteuid()) toys.optflags |= FLAG_p;

[enh-google]

(test patch sent to mailing list...)