From: Paulo Alcantara <pc@manguebit.org> stable inclusion from stable-v6.1.167 commit fd4547830720647d4af02ee50f883c4b1cca06e4 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14118 CVE: CVE-2026-31392 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 12b4c5d98cd7ca46d5035a57bcd995df614c14e1 upstream. Customer reported that some of their krb5 mounts were failing against a single server as the client was trying to mount the shares with wrong credentials. It turned out the client was reusing SMB session from first mount to try mounting the other shares, even though a different username= option had been specified to the other mounts. By using username mount option along with sec=krb5 to search for principals from keytab is supported by cifs.upcall(8) since cifs-utils-4.8. So fix this by matching username mount option in match_session() even with Kerberos. For example, the second mount below should fail with -ENOKEY as there is no 'foobar' principal in keytab (/etc/krb5.keytab). The client ends up reusing SMB session from first mount to perform the second one, which is wrong. ``` $ 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 sec=krb5,username=testuser $ mount.cifs //w22-root2/scratch /mnt/2 -o sec=krb5,username=foobar $ mount -t cifs | grep -Po 'username=\K\w+' testuser testuser ``` Reported-by: Oscar Santos <ossantos@redhat.com> Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org> Cc: David Howells <dhowells@redhat.com> Cc: linux-cifs@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Steve French <stfrench@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: fs/cifs/connect.c fs/smb/client/connect.c [Linux has moved cifs to the smb/client.] Signed-off-by: Zizhi Wo <wozizhi@huawei.com> --- fs/cifs/connect.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 287230b70e51..a69f6f1f31bc 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -2737,10 +2737,14 @@ static int match_session(struct cifs_ses *ses, struct smb_vol *vol) switch (ses->sectype) { case Kerberos: if (!uid_eq(vol->cred_uid, ses->cred_uid)) return 0; + if (strncmp(ses->user_name ?: "", + vol->username ?: "", + CIFS_MAX_USERNAME_LEN)) + return 0; break; default: /* NULL username means anonymous session */ if (ses->user_name == NULL) { if (!vol->nullauth) -- 2.39.2