[PATCH 5.10.y 5/5] nvmet-tcp: add bounds checks in nvmet_tcp_build_pdu_iovec

[Sasha Levin <sashal@kernel.org>]

From: YunJe Shin <yjshin0438@gmail.com>

[ Upstream commit 52a0a98549344ca20ad81a4176d68d28e3c05a5c ]

nvmet_tcp_build_pdu_iovec() could walk past cmd->req.sg when a PDU
length or offset exceeds sg_cnt and then use bogus sg->length/offset
values, leading to _copy_to_iter() GPF/KASAN. Guard sg_idx, remaining
entries, and sg->length/offset before building the bvec.

Fixes: 872d26a391da ("nvmet-tcp: add NVMe over TCP target driver")
Signed-off-by: YunJe Shin <ioerts@kookmin.ac.kr>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Joonkyo Jung <joonkyoj@yonsei.ac.kr>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/nvme/target/tcp.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 6fd4f74315f6c..32b239f65529e 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -294,11 +294,14 @@ static void nvmet_tcp_free_cmd_buffers(struct nvmet_tcp_cmd *cmd)
 	cmd->req.sg = NULL;
 }
 
+static void nvmet_tcp_fatal_error(struct nvmet_tcp_queue *queue);
+
 static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
 {
 	struct bio_vec *iov = cmd->iov;
 	struct scatterlist *sg;
 	u32 length, offset, sg_offset;
+	unsigned int sg_remaining;
 	int nr_pages;
 
 	length = cmd->pdu_len;
@@ -306,10 +309,25 @@ static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
 	offset = cmd->rbytes_done;
 	cmd->sg_idx = offset / PAGE_SIZE;
 	sg_offset = offset % PAGE_SIZE;
+	if (!cmd->req.sg_cnt || cmd->sg_idx >= cmd->req.sg_cnt) {
+		nvmet_tcp_fatal_error(cmd->queue);
+		return;
+	}
 	sg = &cmd->req.sg[cmd->sg_idx];
+	sg_remaining = cmd->req.sg_cnt - cmd->sg_idx;
 
 	while (length) {
-		u32 iov_len = min_t(u32, length, sg->length - sg_offset);
+		u32 iov_len;
+
+		if (!sg_remaining) {
+			nvmet_tcp_fatal_error(cmd->queue);
+			return;
+		}
+		if (!sg->length || sg->length <= sg_offset) {
+			nvmet_tcp_fatal_error(cmd->queue);
+			return;
+		}
+		iov_len = min_t(u32, length, sg->length - sg_offset);
 
 		iov->bv_page = sg_page(sg);
 		iov->bv_len = sg->length;
@@ -317,6 +335,7 @@ static void nvmet_tcp_build_pdu_iovec(struct nvmet_tcp_cmd *cmd)
 
 		length -= iov_len;
 		sg = sg_next(sg);
+		sg_remaining--;
 		iov++;
 		sg_offset = 0;
 	}
-- 
2.51.0