linux/fs/cifs/dfs.c
Paulo Alcantara 39a154fc2d cifs: protect access of TCP_Server_Info::{dstaddr,hostname}
Use the appropriate locks to protect access of hostname and dstaddr
fields in cifs_tree_connect() as they might get changed by other
tasks.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>
2023-01-04 09:06:53 -06:00

544 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2022 Paulo Alcantara <palcantara@suse.de>
*/
#include <linux/namei.h>
#include "cifsproto.h"
#include "cifs_debug.h"
#include "dns_resolve.h"
#include "fs_context.h"
#include "dfs.h"
/**
* dfs_parse_target_referral - set fs context for dfs target referral
*
* @full_path: full path in UNC format.
* @ref: dfs referral pointer.
* @ctx: smb3 fs context pointer.
*
* Return zero if dfs referral was parsed correctly, otherwise non-zero.
*/
int dfs_parse_target_referral(const char *full_path, const struct dfs_info3_param *ref,
struct smb3_fs_context *ctx)
{
int rc;
const char *prepath = NULL;
char *path;
if (!full_path || !*full_path || !ref || !ctx)
return -EINVAL;
if (WARN_ON_ONCE(!ref->node_name || ref->path_consumed < 0))
return -EINVAL;
if (strlen(full_path) - ref->path_consumed) {
prepath = full_path + ref->path_consumed;
/* skip initial delimiter */
if (*prepath == '/' || *prepath == '\\')
prepath++;
}
path = cifs_build_devname(ref->node_name, prepath);
if (IS_ERR(path))
return PTR_ERR(path);
rc = smb3_parse_devname(path, ctx);
if (rc)
goto out;
rc = dns_resolve_server_name_to_ip(path, (struct sockaddr *)&ctx->dstaddr, NULL);
out:
kfree(path);
return rc;
}
/*
* cifs_build_path_to_root returns full path to root when we do not have an
* existing connection (tcon)
*/
static char *build_unc_path_to_root(const struct smb3_fs_context *ctx,
const struct cifs_sb_info *cifs_sb, bool useppath)
{
char *full_path, *pos;
unsigned int pplen = useppath && ctx->prepath ? strlen(ctx->prepath) + 1 : 0;
unsigned int unc_len = strnlen(ctx->UNC, MAX_TREE_SIZE + 1);
if (unc_len > MAX_TREE_SIZE)
return ERR_PTR(-EINVAL);
full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
if (full_path == NULL)
return ERR_PTR(-ENOMEM);
memcpy(full_path, ctx->UNC, unc_len);
pos = full_path + unc_len;
if (pplen) {
*pos = CIFS_DIR_SEP(cifs_sb);
memcpy(pos + 1, ctx->prepath, pplen);
pos += pplen;
}
*pos = '\0'; /* add trailing null */
convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
cifs_dbg(FYI, "%s: full_path=%s\n", __func__, full_path);
return full_path;
}
static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
{
struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
int rc;
ctx->leaf_fullpath = (char *)full_path;
rc = cifs_mount_get_session(mnt_ctx);
ctx->leaf_fullpath = NULL;
if (!rc) {
struct cifs_ses *ses = mnt_ctx->ses;
mutex_lock(&ses->session_mutex);
ses->dfs_root_ses = mnt_ctx->root_ses;
mutex_unlock(&ses->session_mutex);
}
return rc;
}
static void set_root_ses(struct cifs_mount_ctx *mnt_ctx)
{
if (mnt_ctx->ses) {
spin_lock(&cifs_tcp_ses_lock);
mnt_ctx->ses->ses_count++;
spin_unlock(&cifs_tcp_ses_lock);
dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, mnt_ctx->ses);
}
mnt_ctx->root_ses = mnt_ctx->ses;
}
static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, const char *full_path,
const struct dfs_cache_tgt_iterator *tit)
{
struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
struct dfs_info3_param ref = {};
int rc;
rc = dfs_cache_get_tgt_referral(ref_path + 1, tit, &ref);
if (rc)
return rc;
rc = dfs_parse_target_referral(full_path + 1, &ref, ctx);
if (rc)
goto out;
cifs_mount_put_conns(mnt_ctx);
rc = get_session(mnt_ctx, ref_path);
if (rc)
goto out;
if (ref.flags & DFSREF_REFERRAL_SERVER)
set_root_ses(mnt_ctx);
rc = -EREMOTE;
if (ref.flags & DFSREF_STORAGE_SERVER) {
rc = cifs_mount_get_tcon(mnt_ctx);
if (rc)
goto out;
/* some servers may not advertise referral capability under ref.flags */
if (!(ref.flags & DFSREF_REFERRAL_SERVER) &&
is_tcon_dfs(mnt_ctx->tcon))
set_root_ses(mnt_ctx);
rc = cifs_is_path_remote(mnt_ctx);
}
out:
free_dfs_info_param(&ref);
return rc;
}
static int __dfs_mount_share(struct cifs_mount_ctx *mnt_ctx)
{
struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
char *ref_path = NULL, *full_path = NULL;
struct dfs_cache_tgt_iterator *tit;
struct TCP_Server_Info *server;
char *origin_fullpath = NULL;
int num_links = 0;
int rc;
ref_path = dfs_get_path(cifs_sb, ctx->UNC);
if (IS_ERR(ref_path))
return PTR_ERR(ref_path);
full_path = build_unc_path_to_root(ctx, cifs_sb, true);
if (IS_ERR(full_path)) {
rc = PTR_ERR(full_path);
full_path = NULL;
goto out;
}
origin_fullpath = kstrdup(full_path, GFP_KERNEL);
if (!origin_fullpath) {
rc = -ENOMEM;
goto out;
}
do {
struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
rc = dfs_get_referral(mnt_ctx, ref_path + 1, NULL, &tl);
if (rc)
break;
tit = dfs_cache_get_tgt_iterator(&tl);
if (!tit) {
cifs_dbg(VFS, "%s: dfs referral (%s) with no targets\n", __func__,
ref_path + 1);
rc = -ENOENT;
dfs_cache_free_tgts(&tl);
break;
}
do {
rc = get_dfs_conn(mnt_ctx, ref_path, full_path, tit);
if (!rc)
break;
if (rc == -EREMOTE) {
if (++num_links > MAX_NESTED_LINKS) {
rc = -ELOOP;
break;
}
kfree(ref_path);
kfree(full_path);
ref_path = full_path = NULL;
full_path = build_unc_path_to_root(ctx, cifs_sb, true);
if (IS_ERR(full_path)) {
rc = PTR_ERR(full_path);
full_path = NULL;
} else {
ref_path = dfs_get_path(cifs_sb, full_path);
if (IS_ERR(ref_path)) {
rc = PTR_ERR(ref_path);
ref_path = NULL;
}
}
break;
}
} while ((tit = dfs_cache_get_next_tgt(&tl, tit)));
dfs_cache_free_tgts(&tl);
} while (rc == -EREMOTE);
if (!rc) {
server = mnt_ctx->server;
mutex_lock(&server->refpath_lock);
server->origin_fullpath = origin_fullpath;
server->current_fullpath = server->leaf_fullpath;
mutex_unlock(&server->refpath_lock);
origin_fullpath = NULL;
}
out:
kfree(origin_fullpath);
kfree(ref_path);
kfree(full_path);
return rc;
}
int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
{
struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
int rc;
*isdfs = false;
rc = get_session(mnt_ctx, NULL);
if (rc)
return rc;
mnt_ctx->root_ses = mnt_ctx->ses;
/*
* If called with 'nodfs' mount option, then skip DFS resolving. Otherwise unconditionally
* try to get an DFS referral (even cached) to determine whether it is an DFS mount.
*
* Skip prefix path to provide support for DFS referrals from w2k8 servers which don't seem
* to respond with PATH_NOT_COVERED to requests that include the prefix.
*/
if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
dfs_get_referral(mnt_ctx, ctx->UNC + 1, NULL, NULL)) {
rc = cifs_mount_get_tcon(mnt_ctx);
if (rc)
return rc;
rc = cifs_is_path_remote(mnt_ctx);
if (!rc || rc != -EREMOTE)
return rc;
}
*isdfs = true;
set_root_ses(mnt_ctx);
return __dfs_mount_share(mnt_ctx);
}
/* Update dfs referral path of superblock */
static int update_server_fullpath(struct TCP_Server_Info *server, struct cifs_sb_info *cifs_sb,
const char *target)
{
int rc = 0;
size_t len = strlen(target);
char *refpath, *npath;
if (unlikely(len < 2 || *target != '\\'))
return -EINVAL;
if (target[1] == '\\') {
len += 1;
refpath = kmalloc(len, GFP_KERNEL);
if (!refpath)
return -ENOMEM;
scnprintf(refpath, len, "%s", target);
} else {
len += sizeof("\\");
refpath = kmalloc(len, GFP_KERNEL);
if (!refpath)
return -ENOMEM;
scnprintf(refpath, len, "\\%s", target);
}
npath = dfs_cache_canonical_path(refpath, cifs_sb->local_nls, cifs_remap(cifs_sb));
kfree(refpath);
if (IS_ERR(npath)) {
rc = PTR_ERR(npath);
} else {
mutex_lock(&server->refpath_lock);
kfree(server->leaf_fullpath);
server->leaf_fullpath = npath;
mutex_unlock(&server->refpath_lock);
server->current_fullpath = server->leaf_fullpath;
}
return rc;
}
static int target_share_matches_server(struct TCP_Server_Info *server, char *share,
bool *target_match)
{
int rc = 0;
const char *dfs_host;
size_t dfs_host_len;
*target_match = true;
extract_unc_hostname(share, &dfs_host, &dfs_host_len);
/* Check if hostnames or addresses match */
cifs_server_lock(server);
if (dfs_host_len != strlen(server->hostname) ||
strncasecmp(dfs_host, server->hostname, dfs_host_len)) {
cifs_dbg(FYI, "%s: %.*s doesn't match %s\n", __func__,
(int)dfs_host_len, dfs_host, server->hostname);
rc = match_target_ip(server, dfs_host, dfs_host_len, target_match);
if (rc)
cifs_dbg(VFS, "%s: failed to match target ip: %d\n", __func__, rc);
}
cifs_server_unlock(server);
return rc;
}
static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
struct cifs_sb_info *cifs_sb, char *tree, bool islink,
struct dfs_cache_tgt_list *tl)
{
int rc;
struct TCP_Server_Info *server = tcon->ses->server;
const struct smb_version_operations *ops = server->ops;
struct cifs_ses *root_ses = CIFS_DFS_ROOT_SES(tcon->ses);
struct cifs_tcon *ipc = root_ses->tcon_ipc;
char *share = NULL, *prefix = NULL;
struct dfs_cache_tgt_iterator *tit;
bool target_match;
tit = dfs_cache_get_tgt_iterator(tl);
if (!tit) {
rc = -ENOENT;
goto out;
}
/* Try to tree connect to all dfs targets */
for (; tit; tit = dfs_cache_get_next_tgt(tl, tit)) {
const char *target = dfs_cache_get_tgt_name(tit);
struct dfs_cache_tgt_list ntl = DFS_CACHE_TGT_LIST_INIT(ntl);
kfree(share);
kfree(prefix);
share = prefix = NULL;
/* Check if share matches with tcp ses */
rc = dfs_cache_get_tgt_share(server->current_fullpath + 1, tit, &share, &prefix);
if (rc) {
cifs_dbg(VFS, "%s: failed to parse target share: %d\n", __func__, rc);
break;
}
rc = target_share_matches_server(server, share, &target_match);
if (rc)
break;
if (!target_match) {
rc = -EHOSTUNREACH;
continue;
}
dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);
if (ipc->need_reconnect) {
scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
rc = ops->tree_connect(xid, ipc->ses, tree, ipc, cifs_sb->local_nls);
cifs_dbg(FYI, "%s: reconnect ipc: %d\n", __func__, rc);
}
scnprintf(tree, MAX_TREE_SIZE, "\\%s", share);
if (!islink) {
rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
break;
}
/*
* If no dfs referrals were returned from link target, then just do a TREE_CONNECT
* to it. Otherwise, cache the dfs referral and then mark current tcp ses for
* reconnect so either the demultiplex thread or the echo worker will reconnect to
* newly resolved target.
*/
if (dfs_cache_find(xid, root_ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
NULL, &ntl)) {
rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
if (rc)
continue;
rc = cifs_update_super_prepath(cifs_sb, prefix);
} else {
/* Target is another dfs share */
rc = update_server_fullpath(server, cifs_sb, target);
dfs_cache_free_tgts(tl);
if (!rc) {
rc = -EREMOTE;
list_replace_init(&ntl.tl_list, &tl->tl_list);
} else
dfs_cache_free_tgts(&ntl);
}
break;
}
out:
kfree(share);
kfree(prefix);
return rc;
}
static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
struct cifs_sb_info *cifs_sb, char *tree, bool islink,
struct dfs_cache_tgt_list *tl)
{
int rc;
int num_links = 0;
struct TCP_Server_Info *server = tcon->ses->server;
char *old_fullpath = server->leaf_fullpath;
do {
rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, islink, tl);
if (!rc || rc != -EREMOTE)
break;
} while (rc = -ELOOP, ++num_links < MAX_NESTED_LINKS);
/*
* If we couldn't tree connect to any targets from last referral path, then
* retry it from newly resolved dfs referral.
*/
if (rc && server->leaf_fullpath != old_fullpath)
cifs_signal_cifsd_for_reconnect(server, true);
dfs_cache_free_tgts(tl);
return rc;
}
int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const struct nls_table *nlsc)
{
int rc;
struct TCP_Server_Info *server = tcon->ses->server;
const struct smb_version_operations *ops = server->ops;
struct super_block *sb = NULL;
struct cifs_sb_info *cifs_sb;
struct dfs_cache_tgt_list tl = DFS_CACHE_TGT_LIST_INIT(tl);
char *tree;
struct dfs_info3_param ref = {0};
/* only send once per connect */
spin_lock(&tcon->tc_lock);
if (tcon->ses->ses_status != SES_GOOD ||
(tcon->status != TID_NEW &&
tcon->status != TID_NEED_TCON)) {
spin_unlock(&tcon->tc_lock);
return 0;
}
tcon->status = TID_IN_TCON;
spin_unlock(&tcon->tc_lock);
tree = kzalloc(MAX_TREE_SIZE, GFP_KERNEL);
if (!tree) {
rc = -ENOMEM;
goto out;
}
if (tcon->ipc) {
cifs_server_lock(server);
scnprintf(tree, MAX_TREE_SIZE, "\\\\%s\\IPC$", server->hostname);
cifs_server_unlock(server);
rc = ops->tree_connect(xid, tcon->ses, tree, tcon, nlsc);
goto out;
}
sb = cifs_get_tcp_super(server);
if (IS_ERR(sb)) {
rc = PTR_ERR(sb);
cifs_dbg(VFS, "%s: could not find superblock: %d\n", __func__, rc);
goto out;
}
cifs_sb = CIFS_SB(sb);
/* If it is not dfs or there was no cached dfs referral, then reconnect to same share */
if (!server->current_fullpath ||
dfs_cache_noreq_find(server->current_fullpath + 1, &ref, &tl)) {
rc = ops->tree_connect(xid, tcon->ses, tcon->tree_name, tcon, cifs_sb->local_nls);
goto out;
}
rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, ref.server_type == DFS_TYPE_LINK,
&tl);
free_dfs_info_param(&ref);
out:
kfree(tree);
cifs_put_tcp_super(sb);
if (rc) {
spin_lock(&tcon->tc_lock);
if (tcon->status == TID_IN_TCON)
tcon->status = TID_NEED_TCON;
spin_unlock(&tcon->tc_lock);
} else {
spin_lock(&tcon->tc_lock);
if (tcon->status == TID_IN_TCON)
tcon->status = TID_GOOD;
spin_unlock(&tcon->tc_lock);
tcon->need_reconnect = false;
}
return rc;
}