[PATCH 4.19 34/50] net/rds: restrict iovecs length for RDS_CMSG_RDMA_ARGS

[Greg Kroah-Hartman]

From: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>

commit a11148e6fcce2ae53f47f0a442d098d860b4f7db upstream.

syzbot found WARNING in rds_rdma_extra_size [1] when RDS_CMSG_RDMA_ARGS
control message is passed with user-controlled
0x40001 bytes of args->nr_local, causing order >= MAX_ORDER condition.

The exact value 0x40001 can be checked with UIO_MAXIOV which is 0x400.
So for kcalloc() 0x400 iovecs with sizeof(struct rds_iovec) = 0x10
is the closest limit, with 0x10 leftover.

Same condition is currently done in rds_cmsg_rdma_args().

[1] WARNING: mm/page_alloc.c:5011
[..]
Call Trace:
 alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
 alloc_pages include/linux/gfp.h:547 [inline]
 kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
 kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
 kmalloc_array include/linux/slab.h:592 [inline]
 kcalloc include/linux/slab.h:621 [inline]
 rds_rdma_extra_size+0xb2/0x3b0 net/rds/rdma.c:568
 rds_rm_size net/rds/send.c:928 [inline]

Reported-by: syzbot+1bd2b07f93745fa38425@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210201203233.1324704-1-snovitoll@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/rds/rdma.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -531,6 +531,9 @@ int rds_rdma_extra_size(struct rds_rdma_
 	if (args->nr_local == 0)
 		return -EINVAL;
 
+	if (args->nr_local > UIO_MAXIOV)
+		return -EMSGSIZE;
+
 	iov->iov = kcalloc(args->nr_local,
 			   sizeof(struct rds_iovec),
 			   GFP_KERNEL);