FAILED: patch "[PATCH] scsi: target: iscsi: Bound iscsi_encode_text_output() appends" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x bf33e01f88388c43e285492a63e539df6ffed64c
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026060410-slam-conch-e2f1@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bf33e01f88388c43e285492a63e539df6ffed64c Mon Sep 17 00:00:00 2001
From: Michael Bommarito <[email protected]>
Date: Mon, 11 May 2026 14:49:14 -0400
Subject: [PATCH] scsi: target: iscsi: Bound iscsi_encode_text_output() appends
to rsp_buf

iscsi_encode_text_output() concatenates "key=value\0" records into login->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check the remaining buffer capacity:

	*length += sprintf(output_buf, "%s=%s", er->key, er->value);
	*length += 1;
	output_buf = textbuf + *length;

The 8192-byte ceiling at iscsi_target_check_login_request() bounds the *input* Login PDU payload, but a single PDU can carry up to 2048 minimal four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte "a=NotUnderstood\0" output record via iscsi_add_notunderstood_response(). 2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB heap overrun in the kmalloc-8k slab.

The fix introduces a static iscsi_encode_text_record() helper that uses snprintf() with a per-call bounds check against the remaining buffer, and threads a u32 textbuf_size parameter through iscsi_encode_text_output(). Both call sites in iscsi_target_handle_csg_zero() (PHASE_SECURITY) and iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls iscsi_release_extra_responses() to drop queued records, and returns -1; both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR / ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning, so the initiator sees an explicit failed-login response rather than a silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL caller did that; the PHASE_SECURITY caller is converted to the same shape.)

index 832588f21f91..b03ed154ca34 100644
@@ -899,10 +899,14 @@ static int iscsi_target_handle_csg_zero(
 			SENDER_TARGET,
 			login->rsp_buf,
 			&login->rsp_length,
+			MAX_KEY_VALUE_PAIRS,
 			conn->param_list,
 			conn->tpg->tpg_attrib.login_keys_workaround);
-	if (ret < 0)
+	if (ret < 0) {
+		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_INITIATOR_ERR,
+				ISCSI_LOGIN_STATUS_INIT_ERR);
 		return -1;
+	}
 
 	if (!iscsi_check_negotiated_keys(conn->param_list)) {
 		bool auth_required = iscsi_conn_auth_required(conn);

@@ -986,6 +990,7 @@ static int iscsi_target_handle_csg_one(struct iscsit_conn *conn, struct iscsi_lo
 			SENDER_TARGET,
 			login->rsp_buf,
 			&login->rsp_length,
+			MAX_KEY_VALUE_PAIRS,
 			conn->param_list,
 			conn->tpg->tpg_attrib.login_keys_workaround);
 	if (ret < 0) {

index c672a971fcb7..38d2238dfe08 100644
@@ -43,7 +43,7 @@ extern struct iscsi_param *iscsi_find_param_from_key(char *, struct iscsi_param_
 extern int iscsi_extract_key_value(char *, char **, char **);
 extern int iscsi_update_param_value(struct iscsi_param *, char *);
 extern int iscsi_decode_text_input(u8, u8, char *, u32, struct iscsit_conn *);
-extern int iscsi_encode_text_output(u8, u8, char *, u32 *,
+extern int iscsi_encode_text_output(u8, u8, char *, u32 *, u32,
 			struct iscsi_param_list *, bool);
 extern int iscsi_check_negotiated_keys(struct iscsi_param_list *);
 extern void iscsi_set_connection_parameters(struct iscsi_conn_ops *,

From: Michael Bommarito <[email protected]>

[ Upstream commit bf33e01f88388c43e285492a63e539df6ffed64c ]

iscsi_encode_text_output() concatenates "key=value\0" records into login->rsp_buf, an 8192-byte kzalloc(MAX_KEY_VALUE_PAIRS) buffer allocated in iscsit_alloc_login_setup_buffer(). The three sprintf() call sites in this function (lines 1398, 1411, 1424 in v7.1-rc2) never check the remaining buffer capacity:

	*length += sprintf(output_buf, "%s=%s", er->key, er->value);
	*length += 1;
	output_buf = textbuf + *length;

The 8192-byte ceiling at iscsi_target_check_login_request() bounds the *input* Login PDU payload, but a single PDU can carry up to 2048 minimal four-byte "a=b\0" pairs, each unknown key expanding to a 16-byte "a=NotUnderstood\0" output record via iscsi_add_notunderstood_response(). 2048 * 16 = 32 KiB of output into an 8 KiB buffer, producing a ~24 KiB heap overrun in the kmalloc-8k slab.

The fix introduces a static iscsi_encode_text_record() helper that uses snprintf() with a per-call bounds check against the remaining buffer, and threads a u32 textbuf_size parameter through iscsi_encode_text_output(). Both call sites in iscsi_target_handle_csg_zero() (PHASE_SECURITY) and iscsi_target_handle_csg_one() (PHASE_OPERATIONAL) pass MAX_KEY_VALUE_PAIRS. On overflow the encoder logs the condition, calls iscsi_release_extra_responses() to drop queued records, and returns -1; both caller sites now emit ISCSI_STATUS_CLS_INITIATOR_ERR / ISCSI_LOGIN_STATUS_INIT_ERR via iscsit_tx_login_rsp() before returning, so the initiator sees an explicit failed-login response rather than a silent connection drop. (Prior to this patch only the PHASE_OPERATIONAL caller did that; the PHASE_SECURITY caller is converted to the same shape.)

---
 drivers/target/iscsi/iscsi_target_nego.c      |  7 ++-
 .../target/iscsi/iscsi_target_parameters.c    | 62 ++++++++++++++-----
 .../target/iscsi/iscsi_target_parameters.h    |  2 +-
 3 files changed, 55 insertions(+), 16 deletions(-)

index 32a2852352db1c..2ff2cbdd2598f9 100644
@@ -870,10 +870,14 @@ static int iscsi_target_handle_csg_zero(
 			SENDER_TARGET,
 			login->rsp_buf,
 			&login->rsp_length,
+			MAX_KEY_VALUE_PAIRS,
 			conn->param_list,
 			conn->tpg->tpg_attrib.login_keys_workaround);
-	if (ret < 0)
+	if (ret < 0) {
+		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_INITIATOR_ERR,
+				ISCSI_LOGIN_STATUS_INIT_ERR);
 		return -1;
+	}
 
 	if (!iscsi_check_negotiated_keys(conn->param_list)) {
 		if (conn->tpg->tpg_attrib.authentication &&

@@ -941,6 +945,7 @@ static int iscsi_target_handle_csg_one(struct iscsi_conn *conn, struct iscsi_log
 			SENDER_TARGET,
 			login->rsp_buf,
 			&login->rsp_length,
+			MAX_KEY_VALUE_PAIRS,
 			conn->param_list,
 			conn->tpg->tpg_attrib.login_keys_workaround);
 	if (ret < 0) {

index 240c4c4344f691..6d02d19eb8cf0f 100644
@@ -46,7 +46,7 @@ extern struct iscsi_param *iscsi_find_param_from_key(char *, struct iscsi_param_
 extern int iscsi_extract_key_value(char *, char **, char **);
 extern int iscsi_update_param_value(struct iscsi_param *, char *);
 extern int iscsi_decode_text_input(u8, u8, char *, u32, struct iscsi_conn *);
-extern int iscsi_encode_text_output(u8, u8, char *, u32 *,
+extern int iscsi_encode_text_output(u8, u8, char *, u32 *, u32,
 			struct iscsi_param_list *, bool);
 extern int iscsi_check_negotiated_keys(struct iscsi_param_list *);
 extern void iscsi_set_connection_parameters(struct iscsi_conn_ops *,

2.53.0