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cifs: fix potential use-after-free bugs

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Ensure that share and prefix variables are set to NULL after kfree()
when looping through DFS targets in __tree_connect_dfs_target().

Also, get rid of @ref in __tree_connect_dfs_target() and just pass a
boolean to indicate whether we're handling link targets or not.

Fixes: c88f7dcd6d64 ("cifs: support nested dfs links over reconnect")
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Paulo Alcantara 2021-11-12 15:16:08 -03:00 committed by Steve French
parent 869da64d07
commit 7f28af9cf5
1 changed files with 19 additions and 22 deletions
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41
fs/cifs/connect.c
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@ -4141,14 +4141,13 @@ static int target_share_matches_server(struct TCP_Server_Info *server, const cha
}
static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
struct cifs_sb_info *cifs_sb, char *tree,
struct dfs_cache_tgt_list *tl, struct dfs_info3_param *ref)
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_tcon *ipc = tcon->ses->tcon_ipc;
bool islink;
char *share = NULL, *prefix = NULL;
const char *tcp_host;
size_t tcp_host_len;
@ -4157,9 +4156,6 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
extract_unc_hostname(server->hostname, &tcp_host, &tcp_host_len);
islink = ref->server_type == DFS_TYPE_LINK;
free_dfs_info_param(ref);
tit = dfs_cache_get_tgt_iterator(tl);
if (!tit) {
rc = -ENOENT;
@ -4173,6 +4169,7 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
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);
@ -4209,25 +4206,23 @@ static int __tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *t
* newly resolved target.
*/
if (dfs_cache_find(xid, tcon->ses, cifs_sb->local_nls, cifs_remap(cifs_sb), target,
ref, &ntl)) {
NULL, &ntl)) {
rc = ops->tree_connect(xid, tcon->ses, tree, tcon, cifs_sb->local_nls);
if (rc)
continue;
rc = dfs_cache_noreq_update_tgthint(server->current_fullpath + 1, tit);
if (!rc)
rc = cifs_update_super_prepath(cifs_sb, prefix);
break;
}
/* 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);
free_dfs_info_param(ref);
/* 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;
}
@ -4240,15 +4235,15 @@ out:
}
static int tree_connect_dfs_target(const unsigned int xid, struct cifs_tcon *tcon,
struct cifs_sb_info *cifs_sb, char *tree,
struct dfs_cache_tgt_list *tl, struct dfs_info3_param *ref)
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;
do {
rc = __tree_connect_dfs_target(xid, tcon, cifs_sb, tree, tl, ref);
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);
@ -4302,7 +4297,9 @@ int cifs_tree_connect(const unsigned int xid, struct cifs_tcon *tcon, const stru
goto out;
}
rc = tree_connect_dfs_target(xid, tcon, cifs_sb, tree, &tl, &ref);
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);