FAILED: Patch "ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off reset in error paths" 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]>.

Thanks,
Sasha

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

From 010eb01ce23b34b50531448b0da391c7f05a72af Mon Sep 17 00:00:00 2001
From: Namjae Jeon <[email protected]>
Date: Sat, 24 Jan 2026 10:55:46 +0900
Subject: [PATCH] ksmbd: fix infinite loop caused by next_smb2_rcv_hdr_off
reset in error paths

The problem occurs when a signed request fails smb2 signature verification check. In __process_request(), if check_sign_req() returns an error, set_smb2_rsp_status(work, STATUS_ACCESS_DENIED) is called. set_smb2_rsp_status() set work->next_smb2_rcv_hdr_off as zero. By resetting next_smb2_rcv_hdr_off to zero, the pointer to the next command in the chain is lost. Consequently, is_chained_smb2_message() continues to point to the same request header instead of advancing. If the header's NextCommand field is non-zero, the function returns true, causing __handle_ksmbd_work() to repeatedly process the same failed request in an infinite loop. This results in the kernel log being flooded with "bad smb2 signature" messages and high CPU usage.

This patch fixes the issue by changing the return value from SERVER_HANDLER_CONTINUE to SERVER_HANDLER_ABORT. This ensures that the processing loop terminates immediately rather than attempting to continue from an invalidated offset.

---
 fs/smb/server/server.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 554ae90df906d..d2410a3f163ae 100644
@@ -126,21 +126,21 @@ static int __process_request(struct ksmbd_work *work, struct ksmbd_conn *conn,
 andx_again:
 	if (command >= conn->max_cmds) {
 		conn->ops->set_rsp_status(work, STATUS_INVALID_PARAMETER);
-		return SERVER_HANDLER_CONTINUE;
+		return SERVER_HANDLER_ABORT;
 	}
 
 	cmds = &conn->cmds[command];
 	if (!cmds->proc) {
 		ksmbd_debug(SMB, "*** not implemented yet cmd = %x\n", command);
 		conn->ops->set_rsp_status(work, STATUS_NOT_IMPLEMENTED);
-		return SERVER_HANDLER_CONTINUE;
+		return SERVER_HANDLER_ABORT;
 	}
 
 	if (work->sess && conn->ops->is_sign_req(work, command)) {
 		ret = conn->ops->check_sign_req(work);
 		if (!ret) {
 			conn->ops->set_rsp_status(work, STATUS_ACCESS_DENIED);
-			return SERVER_HANDLER_CONTINUE;
+			return SERVER_HANDLER_ABORT;
 		}
 	}
 

2.51.0