From f4825922d2fb371e2b969697d792077f1b62b62c Mon Sep 17 00:00:00 2001 From: Sujal Tuladhar Date: Sat, 1 Aug 2026 21:30:00 +0545 Subject: [PATCH] scsi: target: iscsi: Reserve a terminator byte for the login payload iscsi_target_check_login_request() rejects a login PDU whose DataSegmentLength exceeds MAX_KEY_VALUE_PAIRS, but the test is '>' and login->req_buf is allocated with exactly MAX_KEY_VALUE_PAIRS bytes. Since iscsit_get_login_rx() receives payload_length + padding bytes, where padding = ((-payload_length) & 3); any payload_length from 8189 to 8192 fills the whole 8192 byte buffer. The write stays in bounds, but no byte is left for a NUL terminator. The buffer is subsequently consumed as a C string. In the CHAP path chap_check_algorithm() calls kstrdup(a_str), and extract_param() calls strstr(in_buf, pattern) followed by strlen_semi(), none of which take a length. convert_null_to_semi() additionally rewrites every embedded NUL to ';', so even a payload made of well formed NUL separated key=value records is left without a terminator. These walk past the end of the object into adjacent slab memory. It is reachable by an unauthenticated initiator against a portal configured for CHAP; when authentication is not required iscsi_login_zero_tsih_s2() rewrites AuthMethod to None and the CHAP path is never entered. Allocate one extra byte. kzalloc() zeroes it and nothing ever writes to it, as every writer copies to offset 0 for at most MAX_KEY_VALUE_PAIRS bytes, so the buffer is always terminated. Fixes: e48354ce078c ("iscsi-target: Add iSCSI fabric support for target v4.1") Assisted-by: Claude Opus5 (custom harness) Cc: stable@vger.kernel.org Signed-off-by: Sujal Tuladhar Signed-off-by: Martin K. Petersen (Oracle) --- drivers/target/iscsi/iscsi_target_login.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c index aafc94bcb635..c282b6a70296 100644 --- a/drivers/target/iscsi/iscsi_target_login.c +++ b/drivers/target/iscsi/iscsi_target_login.c @@ -47,7 +47,7 @@ static struct iscsi_login *iscsi_login_init_conn(struct iscsit_conn *conn) login->conn = conn; login->first_request = 1; - login->req_buf = kzalloc(MAX_KEY_VALUE_PAIRS, GFP_KERNEL); + login->req_buf = kzalloc(MAX_KEY_VALUE_PAIRS + 1, GFP_KERNEL); if (!login->req_buf) { pr_err("Unable to allocate memory for response buffer.\n"); goto out_login;