virtiofsd: Fix xattr operations

Current virtiofsd has problems about xattr operations and
they does not work properly for directory/symlink/special file.

The fundamental cause is that virtiofsd uses openat() + f...xattr()
systemcalls for xattr operation but we should not open symlink/special
file in the daemon. Therefore the function is restricted.

Fix this problem by:
 1. during setup of each thread, call unshare(CLONE_FS)
 2. in xattr operations (i.e. lo_getxattr), if inode is not a regular
    file or directory, use fchdir(proc_loot_fd) + ...xattr() +
    fchdir(root.fd) instead of openat() + f...xattr()

    (Note: for a regular file/directory openat() + f...xattr()
     is still used for performance reason)

With this patch, xfstests generic/062 passes on virtiofs.

This fix is suggested by Miklos Szeredi and Stefan Hajnoczi.
The original discussion can be found here:
  https://www.redhat.com/archives/virtio-fs/2019-October/msg00046.html

Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Message-Id: <20200227055927.24566-3-misono.tomohiro@jp.fujitsu.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Misono Tomohiro 2020-02-27 14:59:27 +09:00 committed by Dr. David Alan Gilbert
parent 16e15a7308
commit bdfd667883
3 changed files with 77 additions and 47 deletions

View File

@ -426,6 +426,8 @@ err:
return ret;
}
static __thread bool clone_fs_called;
/* Process one FVRequest in a thread pool */
static void fv_queue_worker(gpointer data, gpointer user_data)
{
@ -441,6 +443,17 @@ static void fv_queue_worker(gpointer data, gpointer user_data)
assert(se->bufsize > sizeof(struct fuse_in_header));
if (!clone_fs_called) {
int ret;
/* unshare FS for xattr operation */
ret = unshare(CLONE_FS);
/* should not fail */
assert(ret == 0);
clone_fs_called = true;
}
/*
* An element contains one request and the space to send our response
* They're spread over multiple descriptors in a scatter/gather set

View File

@ -123,7 +123,7 @@ struct lo_inode {
pthread_mutex_t plock_mutex;
GHashTable *posix_locks; /* protected by lo_inode->plock_mutex */
bool is_symlink;
mode_t filetype;
};
struct lo_cred {
@ -695,7 +695,7 @@ static int utimensat_empty(struct lo_data *lo, struct lo_inode *inode,
struct lo_inode *parent;
char path[PATH_MAX];
if (inode->is_symlink) {
if (S_ISLNK(inode->filetype)) {
res = utimensat(inode->fd, "", tv, AT_EMPTY_PATH);
if (res == -1 && errno == EINVAL) {
/* Sorry, no race free way to set times on symlink. */
@ -928,7 +928,8 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
goto out_err;
}
inode->is_symlink = S_ISLNK(e->attr.st_mode);
/* cache only filetype */
inode->filetype = (e->attr.st_mode & S_IFMT);
/*
* One for the caller and one for nlookup (released in
@ -1135,7 +1136,7 @@ static int linkat_empty_nofollow(struct lo_data *lo, struct lo_inode *inode,
struct lo_inode *parent;
char path[PATH_MAX];
if (inode->is_symlink) {
if (S_ISLNK(inode->filetype)) {
res = linkat(inode->fd, "", dfd, name, AT_EMPTY_PATH);
if (res == -1 && (errno == ENOENT || errno == EINVAL)) {
/* Sorry, no race free way to hard-link a symlink. */
@ -2189,12 +2190,6 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
fuse_log(FUSE_LOG_DEBUG, "lo_getxattr(ino=%" PRIu64 ", name=%s size=%zd)\n",
ino, name, size);
if (inode->is_symlink) {
/* Sorry, no race free way to getxattr on symlink. */
saverr = EPERM;
goto out;
}
if (size) {
value = malloc(size);
if (!value) {
@ -2203,12 +2198,25 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
}
sprintf(procname, "%i", inode->fd);
/*
* It is not safe to open() non-regular/non-dir files in file server
* unless O_PATH is used, so use that method for regular files/dir
* only (as it seems giving less performance overhead).
* Otherwise, call fchdir() to avoid open().
*/
if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
ret = fgetxattr(fd, name, value, size);
} else {
/* fchdir should not fail here */
assert(fchdir(lo->proc_self_fd) == 0);
ret = getxattr(procname, name, value, size);
assert(fchdir(lo->root.fd) == 0);
}
if (ret == -1) {
goto out_err;
}
@ -2262,12 +2270,6 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
fuse_log(FUSE_LOG_DEBUG, "lo_listxattr(ino=%" PRIu64 ", size=%zd)\n", ino,
size);
if (inode->is_symlink) {
/* Sorry, no race free way to listxattr on symlink. */
saverr = EPERM;
goto out;
}
if (size) {
value = malloc(size);
if (!value) {
@ -2276,12 +2278,19 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
}
sprintf(procname, "%i", inode->fd);
if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
goto out_err;
}
ret = flistxattr(fd, value, size);
} else {
/* fchdir should not fail here */
assert(fchdir(lo->proc_self_fd) == 0);
ret = listxattr(procname, value, size);
assert(fchdir(lo->root.fd) == 0);
}
if (ret == -1) {
goto out_err;
}
@ -2335,20 +2344,21 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *name,
fuse_log(FUSE_LOG_DEBUG, "lo_setxattr(ino=%" PRIu64
", name=%s value=%s size=%zd)\n", ino, name, value, size);
if (inode->is_symlink) {
/* Sorry, no race free way to setxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = fsetxattr(fd, name, value, size, flags);
} else {
/* fchdir should not fail here */
assert(fchdir(lo->proc_self_fd) == 0);
ret = setxattr(procname, name, value, size, flags);
assert(fchdir(lo->root.fd) == 0);
}
saverr = ret == -1 ? errno : 0;
out:
@ -2383,20 +2393,21 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *name)
fuse_log(FUSE_LOG_DEBUG, "lo_removexattr(ino=%" PRIu64 ", name=%s)\n", ino,
name);
if (inode->is_symlink) {
/* Sorry, no race free way to setxattr on symlink. */
saverr = EPERM;
goto out;
}
sprintf(procname, "%i", inode->fd);
fd = openat(lo->proc_self_fd, procname, O_RDWR);
if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
fd = openat(lo->proc_self_fd, procname, O_RDONLY);
if (fd < 0) {
saverr = errno;
goto out;
}
ret = fremovexattr(fd, name);
} else {
/* fchdir should not fail here */
assert(fchdir(lo->proc_self_fd) == 0);
ret = removexattr(procname, name);
assert(fchdir(lo->root.fd) == 0);
}
saverr = ret == -1 ? errno : 0;
out:
@ -2796,7 +2807,7 @@ static void setup_root(struct lo_data *lo, struct lo_inode *root)
exit(1);
}
root->is_symlink = false;
root->filetype = S_IFDIR;
root->fd = fd;
root->key.ino = stat.st_ino;
root->key.dev = stat.st_dev;

View File

@ -41,6 +41,7 @@ static const int syscall_whitelist[] = {
SCMP_SYS(exit),
SCMP_SYS(exit_group),
SCMP_SYS(fallocate),
SCMP_SYS(fchdir),
SCMP_SYS(fchmodat),
SCMP_SYS(fchownat),
SCMP_SYS(fcntl),
@ -62,7 +63,9 @@ static const int syscall_whitelist[] = {
SCMP_SYS(getpid),
SCMP_SYS(gettid),
SCMP_SYS(gettimeofday),
SCMP_SYS(getxattr),
SCMP_SYS(linkat),
SCMP_SYS(listxattr),
SCMP_SYS(lseek),
SCMP_SYS(madvise),
SCMP_SYS(mkdirat),
@ -85,6 +88,7 @@ static const int syscall_whitelist[] = {
SCMP_SYS(recvmsg),
SCMP_SYS(renameat),
SCMP_SYS(renameat2),
SCMP_SYS(removexattr),
SCMP_SYS(rt_sigaction),
SCMP_SYS(rt_sigprocmask),
SCMP_SYS(rt_sigreturn),
@ -98,10 +102,12 @@ static const int syscall_whitelist[] = {
SCMP_SYS(setresuid32),
#endif
SCMP_SYS(set_robust_list),
SCMP_SYS(setxattr),
SCMP_SYS(symlinkat),
SCMP_SYS(time), /* Rarely needed, except on static builds */
SCMP_SYS(tgkill),
SCMP_SYS(unlinkat),
SCMP_SYS(unshare),
SCMP_SYS(utimensat),
SCMP_SYS(write),
SCMP_SYS(writev),