From 69499395867332364ed4ac8b546537eb3bab6ebb Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Mon, 24 Aug 2026 16:59:12 -0300 Subject: [PATCH] smb: client: fix multiuser mount with krb5 Customer reported that they could no longer mount their SMB shares with multiuser mount option and krb5. Turned out that the client wasn't duplicating username option when creating multiuser connections, therefore failing to retrieve credentials as cifs.upcall(8) couldn't find them in keytab. Fix this by duplicating username option (if set) from original fs context before creating multiuser connections with krb5. Reproducer: ``` $ ktutil ktutil: add_entry -password -p testuser -k 1 -e aes256-cts Password for testuser@ZELDA.TEST: ktutil: write_kt /etc/krb5.keytab ktutil: quit $ klist -ke Keytab name: FILE:/etc/krb5.keytab KVNO Principal ---- ---------------------------------------------------------------- 1 testuser@ZELDA.TEST (aes256-cts-hmac-sha1-96) $ mount.cifs //w22-root2/scratch /mnt/1 -o \ uid=1000,sec=krb5,username=testuser@ZELDA.TEST,multiuser mount error(13): Permission denied Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) and kernel log messages (dmesg) ``` Reported-by: Jacob Shivers Fixes: 12b4c5d98cd7 ("smb: client: fix krb5 mount with username option") Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: Namjae Jeon Cc: stable@vger.kernel.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara --- fs/smb/client/connect.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index bcd7f1ae99ba..b6e98eb31673 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -4189,14 +4189,25 @@ cifs_setup_session(const unsigned int xid, struct cifs_ses *ses, return rc; } -static int -cifs_set_vol_auth(struct smb3_fs_context *ctx, struct cifs_ses *ses) +static int set_fs_context_auth(struct smb3_fs_context *ctx, + struct cifs_ses *ses) { ctx->sectype = ses->sectype; - /* krb5 is special, since we don't need username or pw */ - if (ctx->sectype == Kerberos) + /* + * krb5 is special as we might need to pass username (passwordless) down + * to cifs.upcall(8) for keytab. + */ + if (ctx->sectype == Kerberos) { + if (ses->user_name && ses->user_name[0]) { + ctx->username = kstrndup(ses->user_name, + CIFS_MAX_USERNAME_LEN, + GFP_KERNEL); + if (!ctx->username) + return -ENOMEM; + } return 0; + } return cifs_set_cifscreds(ctx, ses); } @@ -4236,7 +4247,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid) ctx->dfs_root_ses = master_tcon->ses->dfs_root_ses; ctx->unicode = master_tcon->ses->unicode; - rc = cifs_set_vol_auth(ctx, master_tcon->ses); + rc = set_fs_context_auth(ctx, master_tcon->ses); if (rc) { tcon = ERR_PTR(rc); goto out;