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tar-in: Add --no-same-owner flag to tar command when target filesystem doesn't support chown (RHBZ#840572).

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When using tar-in or tools built around it such as virt-make-fs, if
the target filesystem is vfat then unpacking the tarball would fail
because tar tries to chown(2) files and fails.

You would see errors such as:

tar: <file>: Cannot change ownership to uid 500, gid 500: Operation not permitted

This change detects whether the target filesystem supports chown(2).
If not, it adds the --no-same-owner flag to tar to stop it from trying
to change the ownership of newly created files.
This commit is contained in:
Richard W.M. Jones
2012-07-18 12:33:16 +01:00
parent 781857a86b
commit 50780a84f6
1 changed files with 54 additions and 3 deletions
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57
daemon/tar.c
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@@ -36,6 +36,51 @@ optgroup_xz_available (void)
return prog_exists ("xz");
}
/* Detect if chown(2) is supported on the target directory. */
static int
is_chown_supported (const char *dir)
{
size_t len = sysroot_len + strlen (dir) + 64;
char buf[len];
int fd, r, saved_errno;
/* Create a randomly named file. */
snprintf (buf, len, "%s%s/XXXXXXXX.XXX", sysroot, dir);
if (random_name (buf) == -1) {
reply_with_perror ("random_name");
return -1;
}
/* Maybe 'dir' is not a directory or filesystem not writable? */
fd = open (buf, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0666);
if (fd == -1) {
reply_with_perror ("%s", dir);
return -1;
}
/* This is the test. */
r = fchown (fd, 1000, 1000);
saved_errno = errno;
/* Make sure the test file is removed. */
close (fd);
unlink (buf);
if (r == -1 && saved_errno == EPERM) {
/* This means chown is not supported by the filesystem. */
return 0;
}
if (r == -1) {
/* Some other error? */
reply_with_perror_errno (saved_errno, "unexpected error in fchown");
return -1;
}
/* Else chown is supported. */
return 1;
}
/* Read the error file. Returns a string that the caller must free. */
static char *
read_error_file (char *error_file)
@@ -75,7 +120,11 @@ do_tXz_in (const char *dir, const char *filter)
FILE *fp;
char *cmd;
char error_file[] = "/tmp/tarXXXXXX";
int fd;
int fd, chown_supported;
chown_supported = is_chown_supported (dir);
if (chown_supported == -1)
return -1;
fd = mkstemp (error_file);
if (fd == -1) {
@@ -86,8 +135,10 @@ do_tXz_in (const char *dir, const char *filter)
close (fd);
/* "tar -C /sysroot%s -xf -" but we have to quote the dir. */
if (asprintf_nowarn (&cmd, "tar -C %R -%sxf - 2> %s",
dir, filter, error_file) == -1) {
if (asprintf_nowarn (&cmd, "tar -C %R -%sxf - %s2> %s",
dir, filter,
chown_supported ? "" : "--no-same-owner ",
error_file) == -1) {
err = errno;
r = cancel_receive ();
errno = err;