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smb: client: fix mount when dns_resolver key is not available

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There was a wrong assumption that with CONFIG_CIFS_DFS_UPCALL=y there
would always be a dns_resolver key set up so we could unconditionally
upcall to resolve UNC hostname rather than using the value provided by
mount(2).

Only require it when performing automount of junctions within a DFS
share so users that don't have dns_resolver key still can mount their
regular shares with server hostname resolved by mount.cifs(8).

Fixes: 348a04a8d113 ("smb: client: get rid of dfs code dep in namespace.c")
Cc: stable@vger.kernel.org
Tested-by: Eduard Bachmakov <e.bachmakov@gmail.com>
Reported-by: Eduard Bachmakov <e.bachmakov@gmail.com>
Closes: https://lore.kernel.org/all/CADCRUiNvZuiUZ0VGZZO9HRyPyw6x92kiA7o7Q4tsX5FkZqUkKg@mail.gmail.com/
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Paulo Alcantara 2023-11-09 12:01:48 -03:00 committed by Steve French
parent 5923d6686a
commit 5e2fd17f43
3 changed files with 29 additions and 7 deletions
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18
fs/smb/client/dfs.c
View File

@ -263,15 +263,23 @@ out:
return rc;
}
/* Resolve UNC hostname in @ctx->source and set ip addr in @ctx->dstaddr */
/*
* If @ctx->dfs_automount, then update @ctx->dstaddr earlier with the DFS root
* server from where we'll start following any referrals. Otherwise rely on the
* value provided by mount(2) as the user might not have dns_resolver key set up
* and therefore failing to upcall to resolve UNC hostname under @ctx->source.
*/
static int update_fs_context_dstaddr(struct smb3_fs_context *ctx)
{
struct sockaddr *addr = (struct sockaddr *)&ctx->dstaddr;
int rc;
int rc = 0;
rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);
if (!rc)
cifs_set_port(addr, ctx->port);
if (!ctx->nodfs && ctx->dfs_automount) {
rc = dns_resolve_server_name_to_ip(ctx->source, addr, NULL);
if (!rc)
cifs_set_port(addr, ctx->port);
ctx->dfs_automount = false;
}
return rc;
}

1
fs/smb/client/fs_context.h
View File

@ -268,6 +268,7 @@ struct smb3_fs_context {
bool witness:1; /* use witness protocol */
char *leaf_fullpath;
struct cifs_ses *dfs_root_ses;
bool dfs_automount:1; /* set for dfs automount only */
};
extern const struct fs_parameter_spec smb3_fs_parameters[];

17
fs/smb/client/namespace.c
View File

@ -117,6 +117,18 @@ cifs_build_devname(char *nodename, const char *prepath)
return dev;
}
static bool is_dfs_mount(struct dentry *dentry)
{
struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
bool ret;
spin_lock(&tcon->tc_lock);
ret = !!tcon->origin_fullpath;
spin_unlock(&tcon->tc_lock);
return ret;
}
/* Return full path out of a dentry set for automount */
static char *automount_fullpath(struct dentry *dentry, void *page)
{
@ -212,8 +224,9 @@ static struct vfsmount *cifs_do_automount(struct path *path)
ctx->source = NULL;
goto out;
}
cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s\n",
__func__, ctx->source, ctx->UNC, ctx->prepath);
ctx->dfs_automount = is_dfs_mount(mntpt);
cifs_dbg(FYI, "%s: ctx: source=%s UNC=%s prepath=%s dfs_automount=%d\n",
__func__, ctx->source, ctx->UNC, ctx->prepath, ctx->dfs_automount);
mnt = fc_mount(fc);
out: