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authorDaniel Borkmann <daniel@iogearbox.net>2021-10-13 15:21:38 +0200
committerJakub Kicinski <kuba@kernel.org>2021-10-14 19:16:21 -0700
commit507c2f1d2936e07aef83734983a36df01b458ef9 (patch)
tree039b87bb94c7a7a0874ca532bb6711c59b1923a8 /net/core/neighbour.c
parent20d446f24f378ee63a29b259b375691d25002448 (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.c3
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) {