rds_message_map_pages() assigns PAGE_SIZE bytes to every scatterlist entry, even when total_len ends in a partial page. The RDS congestion map is defined as 8192 bytes, so on systems with PAGE_SIZE greater than 8192 the scatterlist maps bytes beyond the end of the congestion map. RDS-TCP transmits the SG contents according to those lengths, so the extra bytes become part of the TCP RDS stream and are interpreted as subsequent RDS message headers, corrupting the stream. Limit the final scatterlist mapping to the number of bytes remaining. This has no effect on systems with a 4K page size and allows RDS-TCP to be used on systems with 16K and larger page sizes. The RDS selftest, which previously hung on 16K pages, now passes. Fixes: 7875e18e0996 ("RDS: Message parsing") Signed-off-by: Greg Marsden --- net/rds/message.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/rds/message.c b/net/rds/message.c index f25f2592586f..47d5e9ab9b10 100644 --- a/net/rds/message.c +++ b/net/rds/message.c @@ -431,7 +431,9 @@ struct rds_message *rds_message_map_pages(unsigned long *page_addrs, unsigned in for (i = 0; i < rm->data.op_nents; ++i) { sg_set_page(&rm->data.op_sg[i], virt_to_page((void *)page_addrs[i]), - PAGE_SIZE, 0); + i == rm->data.op_nents - 1 + ? total_len - (i * PAGE_SIZE) + : PAGE_SIZE, 0); } return rm; -- 2.51.2