wifi: mac80211: Add __counted_by for struct ieee802_11_elems 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>
Link: https://lore.kernel.org/r/ZSQ/jcmTAf/PKHg/@work
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 70b6870fe5b4f6e157b5c5e8d40e69f08b03c7f3..84df104f272b0180ee468454c3ba7b6752626029 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -1746,7 +1746,7 @@ struct ieee802_11_elems {
         */
        size_t scratch_len;
        u8 *scratch_pos;
-       u8 scratch[];
+       u8 scratch[] __counted_by(scratch_len);
 };
 
 static inline struct ieee80211_local *hw_to_local(

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index b6be187104415ff3178f87524a1afe37e8ecbe20..ed680120d5a7be39bdf1ca655c3c39da43b16c16 100644 (file)
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -1625,7 +1625,7 @@ ieee802_11_parse_elems_full(struct ieee80211_elems_parse_params *params)
        int nontransmitted_profile_len = 0;
        size_t scratch_len = 3 * params->len;
 
-       elems = kzalloc(sizeof(*elems) + scratch_len, GFP_ATOMIC);
+       elems = kzalloc(struct_size(elems, scratch, scratch_len), GFP_ATOMIC);
        if (!elems)
                return NULL;
        elems->ie_start = params->start;