wifi: hostap: Add __counted_by for struct prism2_download_data and use struct_size()

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 via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.

This code was found with the help of Coccinelle, and audited and
fixed manually.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/ZSRXXvWMMkm7qqRW@work

diff --git a/drivers/net/wireless/intersil/hostap/hostap_download.c b/drivers/net/wireless/intersil/hostap/hostap_download.c
index 3672291ced5c843c808d910beb2159afeff51ceb..5e5bada28b5b9ca3764d52813beec93ed2fee12b 100644 (file)
--- a/drivers/net/wireless/intersil/hostap/hostap_download.c
+++ b/drivers/net/wireless/intersil/hostap/hostap_download.c
@@ -732,8 +732,7 @@ static int prism2_download(local_info_t *local,
                goto out;
        }
 
-       dl = kzalloc(sizeof(*dl) + param->num_areas *
-                    sizeof(struct prism2_download_data_area), GFP_KERNEL);
+       dl = kzalloc(struct_size(dl, data, param->num_areas), GFP_KERNEL);
        if (dl == NULL) {
                ret = -ENOMEM;
                goto out;

diff --git a/drivers/net/wireless/intersil/hostap/hostap_wlan.h b/drivers/net/wireless/intersil/hostap/hostap_wlan.h
index c25cd21d18bd9f7273180984b28b0dc13221942a..f71c0545c0be677100fb0c69bbe0599f613c7a8c 100644 (file)
--- a/drivers/net/wireless/intersil/hostap/hostap_wlan.h
+++ b/drivers/net/wireless/intersil/hostap/hostap_wlan.h
@@ -617,7 +617,7 @@ struct prism2_download_data {
                u32 addr; /* wlan card address */
                u32 len;
                u8 *data; /* allocated data */
-       } data[];
+       } data[] __counted_by(num_areas);
 };