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scsi: target: iscsi: Prevent login threads from racing between each other

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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>
This commit is contained in:
Maurizio Lombardi 2023-05-08 18:22:19 +02:00 committed by Martin K. Petersen
parent 98a8c2bf93
commit 2a737d3b8c
1 changed files with 3 additions and 1 deletions
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4
drivers/target/iscsi/iscsi_target_nego.c
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@ -1122,6 +1122,7 @@ 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);
@ -1189,7 +1190,6 @@ 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;
@ -1206,9 +1206,11 @@ 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;
}