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btrfs-progs: prop set: ro->rw and received_uuid

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Implement safety check when a read-only subvolume is getting switched
to read-write and there's received_uuid set.

This prevents accidental breakage of incremental send use case but
allows user to do the rw change anyway but resets the received_uuid in
that case.

As this is implemented entirely in userspace, it's racy and using the
raw ioctl won't prevent it nor reset the received_uuid. A change in the
ioctl implementation might do that in the future.

Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2021-10-01 17:01:05 +02:00
parent 332c193c47
commit 3b90ebc2d7
1 changed files with 61 additions and 0 deletions
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61
cmds/property.c
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@ -22,6 +22,7 @@
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/xattr.h>
#include <uuid/uuid.h>
#include <btrfsutil.h>
#include "cmds/commands.h"
#include "cmds/props.h"
@ -40,6 +41,26 @@
#define ENOATTR ENODATA
#endif
static int subvolume_clear_received_uuid(const char *path)
{
struct btrfs_ioctl_received_subvol_args args = {};
int ret;
int fd;
fd = open(path, O_RDONLY | O_NOATIME);
if (fd == -1)
return -errno;
ret = ioctl(fd, BTRFS_IOC_SET_RECEIVED_SUBVOL, &args);
if (ret == -1) {
close(fd);
return -errno;
}
close(fd);
return 0;
}
static int prop_read_only(enum prop_object_type type,
const char *object,
const char *name,
@ -50,6 +71,10 @@ static int prop_read_only(enum prop_object_type type,
bool read_only;
if (value) {
struct btrfs_util_subvolume_info info = {};
bool is_ro = false;
bool do_clear_received_uuid = false;
if (!strcmp(value, "true")) {
read_only = true;
} else if (!strcmp(value, "false")) {
@ -58,12 +83,48 @@ static int prop_read_only(enum prop_object_type type,
error("invalid value for property: %s", value);
return -EINVAL;
}
err = btrfs_util_get_subvolume_read_only(object, &is_ro);
if (err) {
error_btrfs_util(err);
return -errno;
}
/* No change if already read-only */
if (is_ro && read_only)
return 0;
err = btrfs_util_subvolume_info(object, 0, &info);
if (err)
warning("cannot read subvolume info");
if (is_ro && !uuid_is_null(info.received_uuid)) {
pr_verbose(2, "ro->rw switch but has set receive_uuid");
if (force) {
do_clear_received_uuid = true;
} else {
error(
"cannot flip ro->rw with received_uuid set, use force if you really want that");
return -EPERM;
}
}
if (!is_ro && !uuid_is_null(info.received_uuid))
warning("read-write subvolume with received_uuid, this is bad");
err = btrfs_util_set_subvolume_read_only(object, read_only);
if (err) {
error_btrfs_util(err);
return -errno;
}
if (do_clear_received_uuid) {
int ret;
char uuid_str[BTRFS_UUID_UNPARSED_SIZE];
uuid_unparse(info.received_uuid, uuid_str);
pr_verbose(2, "force used, clearing received_uuid, previously %s",
uuid_str);
ret = subvolume_clear_received_uuid(object);
if (ret < 0)
warning("failed to clear received_uuid: %m");
}
} else {
err = btrfs_util_get_subvolume_read_only(object, &read_only);
if (err) {