On 10/9/23 21:54, Kees Cook wrote:
On Mon, Oct 09, 2023 at 01:41:18PM -0600, Gustavo A. R. Silva wrote:
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@xxxxxxxxxx>
---
drivers/net/wireless/intersil/hostap/hostap_download.c | 3 +--
drivers/net/wireless/intersil/hostap/hostap_wlan.h | 2 +-
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/net/wireless/intersil/hostap/hostap_download.c b/drivers/net/wireless/intersil/hostap/hostap_download.c
index 3672291ced5c..5e5bada28b5b 100644
--- 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 c25cd21d18bd..f71c0545c0be 100644
--- 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);
};
Should this be considered a v2 of:
https://lore.kernel.org/linux-hardening/94848cc3-6f5c-46d7-8cc7-98a4f10865b3@xxxxxxxxxxxxxx/
?
Oops... sorry, I forgot I had reviewed this patch of yours.
Yours is more complete since it includes the struct_size() change...
Should I resend this explicitly marking it as a v2?
--
Gustavo
