This is a note to let you know that I've just added the patch titled cifs: Fix preauth hash corruption to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cifs-fix-preauth-hash-corruption.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 05946d4b7a7349ae58bfa2d51ae832e64a394c2d Mon Sep 17 00:00:00 2001 From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> Date: Wed, 10 Mar 2021 13:20:40 +0100 Subject: cifs: Fix preauth hash corruption From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> commit 05946d4b7a7349ae58bfa2d51ae832e64a394c2d upstream. smb311_update_preauth_hash() uses the shash in server->secmech without appropriate locking, and this can lead to sessions corrupting each other's preauth hashes. The following script can easily trigger the problem: #!/bin/sh -e NMOUNTS=10 for i in $(seq $NMOUNTS); mkdir -p /tmp/mnt$i umount /tmp/mnt$i 2>/dev/null || : done while :; do for i in $(seq $NMOUNTS); do mount -t cifs //192.168.0.1/test /tmp/mnt$i -o ... & done wait for i in $(seq $NMOUNTS); do umount /tmp/mnt$i done done Usually within seconds this leads to one or more of the mounts failing with the following errors, and a "Bad SMB2 signature for message" is seen in the server logs: CIFS: VFS: \\192.168.0.1 failed to connect to IPC (rc=-13) CIFS: VFS: cifs_mount failed w/return code = -13 Fix it by holding the server mutex just like in the other places where the shashes are used. Fixes: 8bd68c6e47abff34e4 ("CIFS: implement v3.11 preauth integrity") Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> CC: <stable@xxxxxxxxxxxxxxx> Reviewed-by: Aurelien Aptel <aaptel@xxxxxxxx> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx> [aaptel: backport to kernel without CIFS_SESS_OP] Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/cifs/transport.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/cifs/transport.c +++ b/fs/cifs/transport.c @@ -1171,9 +1171,12 @@ compound_send_recv(const unsigned int xi /* * Compounding is never used during session establish. */ - if ((ses->status == CifsNew) || (optype & CIFS_NEG_OP)) + if ((ses->status == CifsNew) || (optype & CIFS_NEG_OP)) { + mutex_lock(&server->srv_mutex); smb311_update_preauth_hash(ses, rqst[0].rq_iov, rqst[0].rq_nvec); + mutex_unlock(&server->srv_mutex); + } for (i = 0; i < num_rqst; i++) { rc = wait_for_response(server, midQ[i]); @@ -1241,7 +1244,9 @@ compound_send_recv(const unsigned int xi .iov_base = resp_iov[0].iov_base, .iov_len = resp_iov[0].iov_len }; + mutex_lock(&server->srv_mutex); smb311_update_preauth_hash(ses, &iov, 1); + mutex_unlock(&server->srv_mutex); } out: Patches currently in stable-queue which might be from vincent.whitchurch@xxxxxxxx are queue-5.11/cifs-fix-preauth-hash-corruption.patch