From: Kees Cook keescook@chromium.org
[ Upstream commit f8f185e39b4de91bc5235e5be0d829bea69d9b06 ]
The call "skb_copy_from_linear_data(skb, inl + 1, spc)" triggers a FORTIFY memcpy() warning on ppc64 platform:
In function ‘fortify_memcpy_chk’, inlined from ‘skb_copy_from_linear_data’ at ./include/linux/skbuff.h:4029:2, inlined from ‘build_inline_wqe’ at drivers/net/ethernet/mellanox/mlx4/en_tx.c:722:4, inlined from ‘mlx4_en_xmit’ at drivers/net/ethernet/mellanox/mlx4/en_tx.c:1066:3: ./include/linux/fortify-string.h:513:25: error: call to ‘__write_overflow_field’ declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning] 513 | __write_overflow_field(p_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Same behaviour on x86 you can get if you use "__always_inline" instead of "inline" for skb_copy_from_linear_data() in skbuff.h
The call here copies data into inlined tx destricptor, which has 104 bytes (MAX_INLINE) space for data payload. In this case "spc" is known in compile-time but the destination is used with hidden knowledge (real structure of destination is different from that the compiler can see). That cause the fortify warning because compiler can check bounds, but the real bounds are different. "spc" can't be bigger than 64 bytes (MLX4_INLINE_ALIGN), so the data can always fit into inlined tx descriptor. The fact that "inl" points into inlined tx descriptor is determined earlier in mlx4_en_xmit().
Avoid confusing the compiler with "inl + 1" constructions to get to past the inl header by introducing a flexible array "data" to the struct so that the compiler can see that we are not dealing with an array of inl structs, but rather, arbitrary data following the structure. There are no changes to the structure layout reported by pahole, and the resulting machine code is actually smaller.
Reported-by: Josef Oskera joskera@redhat.com Link: https://lore.kernel.org/lkml/20230217094541.2362873-1-joskera@redhat.com Fixes: f68f2ff91512 ("fortify: Detect struct member overflows in memcpy() at compile-time") Cc: Yishai Hadas yishaih@nvidia.com Signed-off-by: Kees Cook keescook@chromium.org Reviewed-by: Tariq Toukan tariqt@nvidia.com Link: https://lore.kernel.org/r/20230218183842.never.954-kees@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mellanox/mlx4/en_tx.c | 22 +++++++++++----------- include/linux/mlx4/qp.h | 1 + 2 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c index c5758637b7bed..2f79378fbf6ec 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c @@ -699,32 +699,32 @@ static void build_inline_wqe(struct mlx4_en_tx_desc *tx_desc, inl->byte_count = cpu_to_be32(1 << 31 | skb->len); } else { inl->byte_count = cpu_to_be32(1 << 31 | MIN_PKT_LEN); - memset(((void *)(inl + 1)) + skb->len, 0, + memset(inl->data + skb->len, 0, MIN_PKT_LEN - skb->len); } - skb_copy_from_linear_data(skb, inl + 1, hlen); + skb_copy_from_linear_data(skb, inl->data, hlen); if (shinfo->nr_frags) - memcpy(((void *)(inl + 1)) + hlen, fragptr, + memcpy(inl->data + hlen, fragptr, skb_frag_size(&shinfo->frags[0]));
} else { inl->byte_count = cpu_to_be32(1 << 31 | spc); if (hlen <= spc) { - skb_copy_from_linear_data(skb, inl + 1, hlen); + skb_copy_from_linear_data(skb, inl->data, hlen); if (hlen < spc) { - memcpy(((void *)(inl + 1)) + hlen, + memcpy(inl->data + hlen, fragptr, spc - hlen); fragptr += spc - hlen; } - inl = (void *) (inl + 1) + spc; - memcpy(((void *)(inl + 1)), fragptr, skb->len - spc); + inl = (void *)inl->data + spc; + memcpy(inl->data, fragptr, skb->len - spc); } else { - skb_copy_from_linear_data(skb, inl + 1, spc); - inl = (void *) (inl + 1) + spc; - skb_copy_from_linear_data_offset(skb, spc, inl + 1, + skb_copy_from_linear_data(skb, inl->data, spc); + inl = (void *)inl->data + spc; + skb_copy_from_linear_data_offset(skb, spc, inl->data, hlen - spc); if (shinfo->nr_frags) - memcpy(((void *)(inl + 1)) + hlen - spc, + memcpy(inl->data + hlen - spc, fragptr, skb_frag_size(&shinfo->frags[0])); } diff --git a/include/linux/mlx4/qp.h b/include/linux/mlx4/qp.h index 9db93e487496a..b6b626157b03a 100644 --- a/include/linux/mlx4/qp.h +++ b/include/linux/mlx4/qp.h @@ -446,6 +446,7 @@ enum {
struct mlx4_wqe_inline_seg { __be32 byte_count; + __u8 data[]; };
enum mlx4_update_qp_attr {