On 9/17/23 18:25, Xiubo Li wrote:
On 9/16/23 04:15, Kees Cook wrote:
Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
As found with Coccinelle[1], add __counted_by for struct ceph_monmap.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.
[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
Cc: Ilya Dryomov <idryomov@xxxxxxxxx>
Cc: Xiubo Li <xiubli@xxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
Cc: ceph-devel@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
include/linux/ceph/mon_client.h | 2 +-
net/ceph/mon_client.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/ceph/mon_client.h b/include/linux/ceph/mon_client.h
index b658961156a0..7a9a40163c0f 100644
--- a/include/linux/ceph/mon_client.h
+++ b/include/linux/ceph/mon_client.h
@@ -19,7 +19,7 @@ struct ceph_monmap {
struct ceph_fsid fsid;
u32 epoch;
u32 num_mon;
- struct ceph_entity_inst mon_inst[];
+ struct ceph_entity_inst mon_inst[] __counted_by(num_mon);
};
struct ceph_mon_client;
diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c
index faabad6603db..f263f7e91a21 100644
--- a/net/ceph/mon_client.c
+++ b/net/ceph/mon_client.c
@@ -1136,6 +1136,7 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
GFP_KERNEL);
if (!monc->monmap)
return -ENOMEM;
+ monc->monmap->num_mon = num_mon;
for (i = 0; i < num_mon; i++) {
struct ceph_entity_inst *inst = &monc->monmap->mon_inst[i];
@@ -1147,7 +1148,6 @@ static int build_initial_monmap(struct ceph_mon_client *monc)
inst->name.type = CEPH_ENTITY_TYPE_MON;
inst->name.num = cpu_to_le64(i);
}
- monc->monmap->num_mon = num_mon;
BTW, is this change related ?
Yes, it is, and it's described in the changelog text.
`num_mon` must be updated before the first access to flex-array `mon_inst`.
Otherwise the compiler cannot properly instrument the code to catch any
out-of-bounds access to `mon_inst`.
--
Gustavo
return 0;
}
Else LGTM.
Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx>
Thanks!
- Xiubo
