diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2021-10-13 15:21:38 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2021-10-14 19:16:21 -0700 |
| commit | 507c2f1d2936e07aef83734983a36df01b458ef9 (patch) | |
| tree | 039b87bb94c7a7a0874ca532bb6711c59b1923a8 /net/core/neighbour.c | |
| parent | 20d446f24f378ee63a29b259b375691d25002448 (diff) | |
net, neigh: Add build-time assertion to avoid neigh->flags overflow
Currently, NDA_FLAGS_EXT flags allow a maximum of 24 bits to be used for
extended neighbor flags. These are eventually fed into neigh->flags by
shifting with NTF_EXT_SHIFT as per commit 2c611ad97a82 ("net, neigh:
Extend neigh->flags to 32 bit to allow for extensions").
If really ever needed in future, the full 32 bits from NDA_FLAGS_EXT can
be used, it would only require to move neigh->flags from u32 to u64 inside
the kernel.
Add a build-time assertion such that when extending the NTF_EXT_MASK with
new bits, we'll trigger an error once we surpass the 24th bit. This assumes
that no bit holes in new NTF_EXT_* flags will slip in from UAPI, but I
think this is reasonable to assume.
Suggested-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/core/neighbour.c')
| -rw-r--r-- | net/core/neighbour.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c index eae73efa9245..4fc601f9cd06 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1940,6 +1940,9 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh, NL_SET_ERR_MSG(extack, "Invalid extended flags"); goto out; } + BUILD_BUG_ON(sizeof(neigh->flags) * BITS_PER_BYTE < + (sizeof(ndm->ndm_flags) * BITS_PER_BYTE + + hweight32(NTF_EXT_MASK))); ndm_flags |= (ext << NTF_EXT_SHIFT); } if (ndm->ndm_ifindex) { |