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mount/btrfs: make check_mountpoint_fd fallback to get_sdev_from_fd

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We face that btrfs returns anonymous device in stat instead of real
superblock dev for volumes, thus all btrfs volume mounts does not pass
check_mountpoint_fd due to dev missmatch between stat and mountinfo. We
can use special helper get_sdev_from_fd instead of stat to try to get
real dev of fd for btrfs.

We move check_mountpoint_fd from open_mountpoint into get_clean_fd and
ns_open_mountpoint to the point where temporary mount we open fd to is
still in mountinfo, thus get_sdev_from_fd would be able to find tmp
mount in mountinfo.

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
This commit is contained in:
Pavel Tikhomirov 2021-12-16 12:57:23 +03:00 • committed by Andrei Vagin
parent bbf5f642de
commit 8ec214d3cb
2 changed files with 46 additions and 4 deletions
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1
criu/include/mount.h
View file

@ -109,6 +109,7 @@ extern int mntns_get_root_by_mnt_id(int mnt_id);
extern struct ns_id *lookup_nsid_by_mnt_id(int mnt_id);
extern int open_mount(unsigned int s_dev);
extern int __check_mountpoint_fd(struct mount_info *pm, int mnt_fd, bool parse_mountinfo);
extern int check_mountpoint_fd(struct mount_info *pm, int mnt_fd);
extern int __open_mountpoint(struct mount_info *pm);
extern int mnt_is_dir(struct mount_info *pm);

49
criu/mount.c
View file

@ -1018,10 +1018,11 @@ int mnt_is_dir(struct mount_info *pm)
return 0;
}
int check_mountpoint_fd(struct mount_info *pm, int mnt_fd)
int __check_mountpoint_fd(struct mount_info *pm, int mnt_fd, bool parse_mountinfo)
{
struct stat st;
int ret, dev;
unsigned int dev;
int ret;
ret = fstat(mnt_fd, &st);
if (ret < 0) {
@ -1042,6 +1043,14 @@ int check_mountpoint_fd(struct mount_info *pm, int mnt_fd)
* allocates new device ID).
*/
if (dev != pm->s_dev_rt) {
/*
* For btrfs device numbers in stat and mountinfo can be
* different, fallback to get_sdev_from_fd to get right dev.
*/
if (!strcmp(pm->fstype->name, "btrfs") && !get_sdev_from_fd(mnt_fd, &dev, parse_mountinfo) &&
dev == pm->s_dev_rt)
return 0;
pr_err("The file system %#x %#x (%#x) %s %s is inaccessible\n", pm->s_dev, pm->s_dev_rt, dev,
pm->fstype->name, pm->ns_mountpoint);
return -1;
@ -1050,6 +1059,11 @@ int check_mountpoint_fd(struct mount_info *pm, int mnt_fd)
return 0;
}
int check_mountpoint_fd(struct mount_info *pm, int mnt_fd)
{
return __check_mountpoint_fd(pm, mnt_fd, false);
}
/*
* mnt_fd is a file descriptor on the mountpoint, which is closed in an error case.
* If mnt_fd is -1, the mountpoint will be opened by this function.
@ -1114,12 +1128,34 @@ static int get_clean_fd(struct mount_info *mi)
char *mnt_path = NULL;
char mnt_path_tmp[] = "/tmp/cr-tmpfs.XXXXXX";
char mnt_path_root[] = "/cr-tmpfs.XXXXXX";
int fd;
mnt_path = get_clean_mnt(mi, mnt_path_tmp, mnt_path_root);
if (!mnt_path)
return -1;
return open_detach_mount(mnt_path);
fd = open(mnt_path, O_RDONLY | O_DIRECTORY, 0);
if (fd < 0) {
pr_perror("Can't open directory %s", mnt_path);
} else {
if (__check_mountpoint_fd(mi, fd, true))
goto err_close;
}
if (umount2(mnt_path, MNT_DETACH)) {
pr_perror("Can't detach mount %s", mnt_path);
goto err_close;
}
if (rmdir(mnt_path)) {
pr_perror("Can't remove tmp dir %s", mnt_path);
goto err_close;
}
return fd;
err_close:
close_safe(&fd);
return -1;
}
/*
@ -1337,6 +1373,11 @@ int ns_open_mountpoint(void *arg)
goto err;
}
if (__check_mountpoint_fd(mi, *fd, true)) {
close(*fd);
goto err;
}
return 0;
err:
return 1;
@ -1411,7 +1452,7 @@ int open_mountpoint(struct mount_info *pm)
goto err;
}
return fd < 0 ? __open_mountpoint(pm) : check_mountpoint_fd(pm, fd);
return fd < 0 ? __open_mountpoint(pm) : fd;
err:
if (ns_old >= 0)
/* coverity[check_return] */