[SRU][F/gke][F/gkeop][PATCH v2 1/1] scsi: iscsi: iscsi_tcp: Avoid holding spinlock while calling getpeername()

[Tim Gardner]

Why isn't this patch destined for focal:linux from which linux-gke and 
linux-gkeop are derived ?

rtg

On 4/1/21 8:10 PM, Khalid Elmously wrote:
> From: Mark Mielke <mark.mielke at gmail.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1921825
> 
> The kernel may fail to boot or devices may fail to come up when
> initializing iscsi_tcp devices starting with Linux 5.8.
> 
> Commit a79af8a64d39 ("[SCSI] iscsi_tcp: use iscsi_conn_get_addr_param
> libiscsi function") introduced getpeername() within the session spinlock.
> 
> Commit 1b66d253610c ("bpf: Add get{peer, sock}name attach types for
> sock_addr") introduced BPF_CGROUP_RUN_SA_PROG_LOCK() within getpeername(),
> which acquires a mutex and when used from iscsi_tcp devices can now lead to
> "BUG: scheduling while atomic:" and subsequent damage.
> 
> Ensure that the spinlock is released before calling getpeername() or
> getsockname(). sock_hold() and sock_put() are used to ensure that the
> socket reference is preserved until after the getpeername() or
> getsockname() complete.
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1877345
> Link: https://lkml.org/lkml/2020/7/28/1085
> Link: https://lkml.org/lkml/2020/8/31/459
> Link: https://lore.kernel.org/r/20200928043329.606781-1-mark.mielke@gmail.com
> Fixes: a79af8a64d39 ("[SCSI] iscsi_tcp: use iscsi_conn_get_addr_param libiscsi function")
> Fixes: 1b66d253610c ("bpf: Add get{peer, sock}name attach types for sock_addr")
> Cc: stable at vger.kernel.org
> Reported-by: Marc Dionne <marc.c.dionne at gmail.com>
> Tested-by: Marc Dionne <marc.c.dionne at gmail.com>
> Reviewed-by: Mike Christie <michael.christie at oracle.com>
> Signed-off-by: Mark Mielke <mark.mielke at gmail.com>
> Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
> (cherry picked from commit bcf3a2953d36bbfb9bd44ccb3db0897d935cc485)
> Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
> ---
>   drivers/scsi/iscsi_tcp.c | 22 +++++++++++++++-------
>   1 file changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
> index b5dd1caae5e9..d10efb66cf19 100644
> --- a/drivers/scsi/iscsi_tcp.c
> +++ b/drivers/scsi/iscsi_tcp.c
> @@ -736,6 +736,7 @@ static int iscsi_sw_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
>   	struct iscsi_tcp_conn *tcp_conn = conn->dd_data;
>   	struct iscsi_sw_tcp_conn *tcp_sw_conn = tcp_conn->dd_data;
>   	struct sockaddr_in6 addr;
> +	struct socket *sock;
>   	int rc;
>   
>   	switch(param) {
> @@ -747,13 +748,17 @@ static int iscsi_sw_tcp_conn_get_param(struct iscsi_cls_conn *cls_conn,
>   			spin_unlock_bh(&conn->session->frwd_lock);
>   			return -ENOTCONN;
>   		}
> +		sock = tcp_sw_conn->sock;
> +		sock_hold(sock->sk);
> +		spin_unlock_bh(&conn->session->frwd_lock);
> +
>   		if (param == ISCSI_PARAM_LOCAL_PORT)
> -			rc = kernel_getsockname(tcp_sw_conn->sock,
> +			rc = kernel_getsockname(sock,
>   						(struct sockaddr *)&addr);
>   		else
> -			rc = kernel_getpeername(tcp_sw_conn->sock,
> +			rc = kernel_getpeername(sock,
>   						(struct sockaddr *)&addr);
> -		spin_unlock_bh(&conn->session->frwd_lock);
> +		sock_put(sock->sk);
>   		if (rc < 0)
>   			return rc;
>   
> @@ -775,6 +780,7 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
>   	struct iscsi_tcp_conn *tcp_conn;
>   	struct iscsi_sw_tcp_conn *tcp_sw_conn;
>   	struct sockaddr_in6 addr;
> +	struct socket *sock;
>   	int rc;
>   
>   	switch (param) {
> @@ -789,16 +795,18 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
>   			return -ENOTCONN;
>   		}
>   		tcp_conn = conn->dd_data;
> -
>   		tcp_sw_conn = tcp_conn->dd_data;
> -		if (!tcp_sw_conn->sock) {
> +		sock = tcp_sw_conn->sock;
> +		if (!sock) {
>   			spin_unlock_bh(&session->frwd_lock);
>   			return -ENOTCONN;
>   		}
> +		sock_hold(sock->sk);
> +		spin_unlock_bh(&session->frwd_lock);
>   
> -		rc = kernel_getsockname(tcp_sw_conn->sock,
> +		rc = kernel_getsockname(sock,
>   					(struct sockaddr *)&addr);
> -		spin_unlock_bh(&session->frwd_lock);
> +		sock_put(sock->sk);
>   		if (rc < 0)
>   			return rc;
>   
> 

-- 
-----------
Tim Gardner
Canonical, Inc