[PATCH AUTOSEL 5.15 02/10] scsi: target: iscsi: Prevent login threads from racing between each other

Sasha Levin
2023-06-15T11:42:55Z

From: Maurizio Lombardi <mlombard@redhat.com>

[ Upstream commit 2a737d3b8c792400118d6cf94958f559de9c5e59 ]

The tpg->np_login_sem is a semaphore that is used to serialize the login
process when multiple login threads run concurrently against the same
target portal group.

The iscsi_target_locate_portal() function finds the tpg, calls
iscsit_access_np() against the np_login_sem semaphore and saves the tpg
pointer in conn->tpg;

If iscsi_target_locate_portal() fails, the caller will check for the
conn->tpg pointer and, if it's not NULL, then it will assume that
iscsi_target_locate_portal() called iscsit_access_np() on the semaphore.

Make sure that conn->tpg gets initialized only if iscsit_access_np() was
successful, otherwise iscsit_deaccess_np() may end up being called against
a semaphore we never took, allowing more than one thread to access the same
tpg.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Link: https://lore.kernel.org/r/20230508162219.1731964-4-mlombard@redhat.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/target/iscsi/iscsi_target_nego.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/target/iscsi/iscsi_target_nego.c b/drivers/target/iscsi/iscsi_target_nego.c
index c0ed6f8e5c5b9..32a2852352db1 100644
--- a/drivers/target/iscsi/iscsi_target_nego.c
+++ b/drivers/target/iscsi/iscsi_target_nego.c
@@ -1071,6 +1071,7 @@ int iscsi_target_locate_portal(
iscsi_target_set_sock_callbacks(conn);

login->np = np;
+ conn->tpg = NULL;

login_req = (struct iscsi_login_req *) login->req;
payload_length = ntoh24(login_req->dlength);
@@ -1138,7 +1139,6 @@ int iscsi_target_locate_portal(
*/
sessiontype = strncmp(s_buf, DISCOVERY, 9);
if (!sessiontype) {
- conn->tpg = iscsit_global->discovery_tpg;
if (!login->leading_connection)
goto get_target;

@@ -1155,9 +1155,11 @@ int iscsi_target_locate_portal(
* Serialize access across the discovery struct iscsi_portal_group to
* process login attempt.
*/
+ conn->tpg = iscsit_global->discovery_tpg;
if (iscsit_access_np(np, conn->tpg) < 0) {
iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
ISCSI_LOGIN_STATUS_SVC_UNAVAILABLE);
+ conn->tpg = NULL;
ret = -1;
goto out;
}
--
2.39.2