nvmet-tcp: fix out-of-bounds access when receiving multiple h2cdata PDUs

When the host sends multiple h2cdata PDUs, we keep track on
the receive progress and calculate the scatterlist index and
offsets.

The issue is that sg_offset should only be kept for the first
iov entry we map in the iovec as this is the difference between
our cursor and the sg entry offset itself.

In addition, the sg index was calculated wrong because we should
not round up when dividing the command byte offset with PAG_SIZE.

Fixes: 872d26a391da ("nvmet-tcp: add NVMe over TCP target driver")
Reported-by: Narayan Ayalasomayajula <Narayan.Ayalasomayajula@wdc.com>
Tested-by: Narayan Ayalasomayajula <Narayan.Ayalasomayajula@wdc.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index dc1f0f6471896e3dfd3f38dee4084184bc5d588c..aacf06f0b4312539c0d295d96ce5a2d7542c7c17 100644 (file)
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -305,7 +305,7 @@ static void nvmet_tcp_map_pdu_iovec(struct nvmet_tcp_cmd *cmd)
        length = cmd->pdu_len;
        cmd->nr_mapped = DIV_ROUND_UP(length, PAGE_SIZE);
        offset = cmd->rbytes_done;
-       cmd->sg_idx = DIV_ROUND_UP(offset, PAGE_SIZE);
+       cmd->sg_idx = offset / PAGE_SIZE;
        sg_offset = offset % PAGE_SIZE;
        sg = &cmd->req.sg[cmd->sg_idx];
 
@@ -318,6 +318,7 @@ static void nvmet_tcp_map_pdu_iovec(struct nvmet_tcp_cmd *cmd)
                length -= iov_len;
                sg = sg_next(sg);
                iov++;
+               sg_offset = 0;
        }
 
        iov_iter_kvec(&cmd->recv_msg.msg_iter, READ, cmd->iov,