[Devel] [PATCH 3/6] run modified tar if upstream

[Kir Kolyshkin]

On 03/11/2013 04:01 AM, Glauber Costa wrote:
> If we are running upstream with user namespaces, we need to run a modified
> version of tar to extract the files. To avoid compatibility problems, we will
> resort to LD_PRELOAD if a recent tar is not available (if ever).
>
> Signed-off-by: Glauber Costa <glommer at parallels.com>
> ---
>   scripts/vps-create.in   | 18 ++++++++++++
>   src/lib/Makefile.am     |  3 ++
>   src/lib/chown_preload.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
>   src/lib/create.c        | 17 ++++++++----
>   4 files changed, 106 insertions(+), 5 deletions(-)
>   create mode 100644 src/lib/chown_preload.c
>
> diff --git a/scripts/vps-create.in b/scripts/vps-create.in
> index 126f048..08edfbe 100755
> --- a/scripts/vps-create.in
> +++ b/scripts/vps-create.in
> @@ -22,11 +22,26 @@
>   # Required parameters:
>   #   VE_PRVT		- path to root of CT private areas
>   #   PRIVATE_TEMPLATE	- path to private template used as a source for copying
> +#
> +# Optional parameters:
> +#   UID_OFFSET		- offset to be added to all tar UIDs
> +#   GID_OFFSET		- offset to be added to all tar GIDs
>   
>   . @SCRIPTDIR@/vps-functions
>   
>   vzcheckvar VE_PRVT PRIVATE_TEMPLATE
>   
> +chown_preload_if_needed()
> +{
> +	if [ "xUID_OFFSET" == "x" ]; then return; fi
> +	if [ "xGID_OFFSET" == "x" ]; then return; fi
> +
> +	# The goal is to get this merged into tar so we no longer
> +	# need to do this preload. Whenever it happens, we will include
> +	# a version check here as well
> +	export LD_PRELOAD=libvzchown.so
> +}
> +
>   create_prvt()
>   {
>   	local TMP AVAIL NEEDED HEADER OPT
> @@ -75,6 +90,9 @@ create_prvt()
>   	[ "$AVAIL" -ge "$NEEDED" ] ||
>   		vzerror "Insufficient disk space in $VE_PRVT; available: $AVAIL, needed: $NEEDED" ${VZ_FS_NO_DISK_SPACE}
>   	CAT=cat
> +
> +	chown_preload_if_needed
> +
>   	# Use pv to show nice progress bar if we can
>   	pv -V >/dev/null 2>&1 && CAT=pv
>   	chmod 700 "$VE_PRVT"
> diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am
> index 42a7ed6..429de7f 100644
> --- a/src/lib/Makefile.am
> +++ b/src/lib/Makefile.am
> @@ -70,6 +70,9 @@ libvzctl_la_LIBADD = $(XML_LIBS) $(CGROUP_LIBS) $(DL_LIBS)
>   
>   if HAVE_CGROUP
>   libvzctl_la_SOURCES += cgroup.c hooks_ct.c
> +
> +lib_LTLIBRARIES += libvzchown.la
> +libvzchown_la_SOURCES = chown_preload.c
>   endif
>   
>   if HAVE_VZ_KERNEL
> diff --git a/src/lib/chown_preload.c b/src/lib/chown_preload.c
> new file mode 100644
> index 0000000..0bc5d0d
> --- /dev/null
> +++ b/src/lib/chown_preload.c
> @@ -0,0 +1,73 @@
> +#include <unistd.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +#include <dlfcn.h>
> +
> +static int (*real_chown)(const char *path, uid_t owner, gid_t group) = NULL;
> +static int (*real_fchown)(int fd, uid_t owner, gid_t group) = NULL;
> +static int (*real_lchown)(const char *path, uid_t owner, gid_t group) = NULL;
> +static int (*real_fchownat)(int dirfd, const char *pathname,
> +		uid_t owner, gid_t group, int flags) = NULL;
> +
> +uid_t uid_offset = 0;
> +gid_t gid_offset = 0;
> +
> +static void __init(void)
> +{
> +	char *uidstr, *gidstr;
> +
> +	uidstr = getenv("UID_OFFSET");
> +	gidstr = getenv("GID_OFFSET");
> +	if (!uidstr || !gidstr) {
> +		fprintf(stderr, "Environment variables UID_OFFSET "
> +				"and GID_OFFSET are required -- aborting\n");
> +		exit(33);
> +	}
> +	uid_offset = strtol(uidstr, NULL, 10);
> +	gid_offset = strtol(gidstr, NULL, 10);
> +
> +	real_chown = dlsym(RTLD_NEXT, "chown");
> +	real_fchown = dlsym(RTLD_NEXT, "fchown");
> +	real_lchown = dlsym(RTLD_NEXT, "lchown");
> +	real_fchownat = dlsym(RTLD_NEXT, "fchownat");
> +
> +	if (!real_chown || !real_fchown || !real_lchown || !real_fchownat) {
> +		fprintf(stderr, "dlsym failed: %s\n", dlerror());
> +		exit(34);
> +	}
> +}
> +
> +int chown(const char *path, uid_t owner, gid_t group)
> +{
> +	if (!real_chown)
> +		__init();
> +
> +	return real_chown(path, owner + uid_offset, group + gid_offset);
> +}
> +
> +int fchown(int fd, uid_t owner, gid_t group)
> +{
> +	if (!real_fchown)
> +		__init();
> +
> +	return real_fchown(fd, owner + uid_offset, group + gid_offset);
> +}
> +
> +int lchown(const char *path, uid_t owner, gid_t group)
> +{
> +	if (!real_lchown)
> +		__init();
> +
> +	return real_lchown(path, owner + uid_offset, group + gid_offset);
> +}
> +
> +int fchownat(int dirfd, const char *pathname,
> +		uid_t owner, gid_t group, int flags)
> +{
> +	if (!real_fchownat)
> +		__init();
> +
> +	return real_fchownat(dirfd, pathname,
> +			owner + uid_offset, group + gid_offset, flags);
> +}
> diff --git a/src/lib/create.c b/src/lib/create.c
> index 0a0330f..1f22463 100644
> --- a/src/lib/create.c
> +++ b/src/lib/create.c
> @@ -98,7 +98,7 @@ static int fs_create(envid_t veid, vps_handler *h, fs_param *fs,
>   	char buf[PATH_LEN];
>   	int ret;
>   	char *arg[2];
> -	char *env[4];
> +	char *env[6];
>   	int quota = 0;
>   	int i;
>   	char *dst;
> @@ -196,11 +196,18 @@ find:
>   	arg[0] = VPS_CREATE;
>   	arg[1] = NULL;
>   	snprintf(buf, sizeof(buf), "PRIVATE_TEMPLATE=%s", tarball);
> -	env[0] = strdup(buf);
> +	i = 0;
> +	env[i++] = strdup(buf);
>   	snprintf(buf, sizeof(buf), "VE_PRVT=%s", dst);
> -	env[1] = strdup(buf);
> -	env[2] = strdup(ENV_PATH);
> -	env[3] = NULL;
> +	env[i++] = strdup(buf);
> +	if (!is_vz_kernel(h) && h->can_join_userns) {

Also, since you introduce can_join_userns in the next patch, this makes 
this one non-bisectable.
Please reorder properly.

> +		snprintf(buf, sizeof(buf), "UID_OFFSET=%d", uid_offset);
> +		env[i++] = strdup(buf);
> +		snprintf(buf, sizeof(buf), "GID_OFFSET=%d", gid_offset);
> +		env[i++] = strdup(buf);
> +	}
> +	env[i++] = strdup(ENV_PATH);
> +	env[i] = NULL;
>   	logger(0, 0, "Creating container private area (%s)", tmpl->ostmpl);
>   	ret = run_script(VPS_CREATE, arg, env, 0);
>   	free_arg(env);