[PATCH 5.15 099/177] netdevsim: Zero-initialize memory for new maps value in function nsim_bpf_map_alloc

[Greg Kroah-Hartman]

From: Haimin Zhang <tcs.kernel@xxxxxxxxx>

[ Upstream commit 481221775d53d6215a6e5e9ce1cce6d2b4ab9a46 ]

Zero-initialize memory for new map's value in function nsim_bpf_map_alloc
since it may cause a potential kernel information leak issue, as follows:
1. nsim_bpf_map_alloc calls nsim_map_alloc_elem to allocate elements for
a new map.
2. nsim_map_alloc_elem uses kmalloc to allocate map's value, but doesn't
zero it.
3. A user application can use IOCTL BPF_MAP_LOOKUP_ELEM to get specific
element's information in the map.
4. The kernel function map_lookup_elem will call bpf_map_copy_value to get
the information allocated at step-2, then use copy_to_user to copy to the
user buffer.
This can only leak information for an array map.

Fixes: 395cacb5f1a0 ("netdevsim: bpf: support fake map offload")
Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Acked-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Haimin Zhang <tcs.kernel@xxxxxxxxx>
Link: https://lore.kernel.org/r/20211215111530.72103-1-tcs.kernel@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/netdevsim/bpf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/netdevsim/bpf.c b/drivers/net/netdevsim/bpf.c
index 90aafb56f1409..a438202129323 100644
--- a/drivers/net/netdevsim/bpf.c
+++ b/drivers/net/netdevsim/bpf.c
@@ -514,6 +514,7 @@ nsim_bpf_map_alloc(struct netdevsim *ns, struct bpf_offloaded_map *offmap)
 				goto err_free;
 			key = nmap->entry[i].key;
 			*key = i;
+			memset(nmap->entry[i].value, 0, offmap->map.value_size);
 		}
 	}
 
-- 
2.33.0