From bce07e2f37b5e4a427d36fd6b1c14067b27591db Mon Sep 17 00:00:00 2001 From: Yehyeong Lee Date: Sat, 1 Aug 2026 22:36:35 +0900 Subject: [PATCH] scsi: libiscsi_tcp: Check the data direction of a Data-In PDU The Data-In branch of iscsi_tcp_hdr_dissect() resolves the ITT to a task and copies the PDU's data segment into that command's scatterlist without asking whether the command was reading. iscsi_tcp_r2t_rsp() in the same file does ask, and rejects an R2T for a command that is not DMA_TO_DEVICE. A target that answers a WRITE command's ITT with a Data-In therefore has the initiator write target-supplied bytes into the pages that write was about to send. Those are the caller's own pinned pages for an O_DIRECT write, and page cache pages for a buffered one. Observed against a test target that emits one 512-byte Data-In naming a 128 KB write's ITT, after the R2T for that write. With O_DIRECT the caller's buffer ends up holding 512 bytes of the target's data while pwrite() returns 131072. Buffered is quieter: pwrite() and fsync() both succeed, nothing is logged, and reading those blocks back returns the target's bytes out of the page cache without a command going on the wire. Check the direction before using the scatterlist, the way the R2T path already does. Cc: stable@vger.kernel.org Signed-off-by: Yehyeong Lee Reviewed-by: Mike Christie Link: https://patch.msgid.link/20260801133635.1986706-1-yhlee@isslab.korea.ac.kr Fixes: a081c13e39b5 ("[SCSI] iscsi_tcp: split module into lib and lld") Signed-off-by: Martin K. Petersen (Oracle) --- drivers/scsi/libiscsi_tcp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/scsi/libiscsi_tcp.c b/drivers/scsi/libiscsi_tcp.c index 7223bb18b048..d35f93451ee9 100644 --- a/drivers/scsi/libiscsi_tcp.c +++ b/drivers/scsi/libiscsi_tcp.c @@ -480,6 +480,9 @@ static int iscsi_tcp_data_in(struct iscsi_conn *conn, struct iscsi_task *task) int datasn = be32_to_cpu(rhdr->datasn); unsigned total_in_length = task->sc->sdb.length; + if (task->sc->sc_data_direction != DMA_FROM_DEVICE) + return ISCSI_ERR_PROTO; + /* * lib iscsi will update this in the completion handling if there * is status.