On 10/9/23 16:55, Jason Andryuk wrote:
Hi,
I randomly peeked at this patch. Unfortunately, I am not familiar
with the actual p54 code.
On Fri, Oct 6, 2023 at 4:17 PM Kees Cook <keescook@xxxxxxxxxxxx> 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).
As found with Coccinelle[1], add __counted_by for struct p54_cal_database.
Cc: Christian Lamparter <chunkeey@xxxxxxxxxxxxxx>
Cc: Kalle Valo <kvalo@xxxxxxxxxx>
Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
Cc: linux-wireless@xxxxxxxxxxxxxxx
Cc: linux-hardening@xxxxxxxxxxxxxxx
Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
drivers/net/wireless/intersil/p54/p54.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/wireless/intersil/p54/p54.h b/drivers/net/wireless/intersil/p54/p54.h
index 3356ea708d81..770e348d1f6c 100644
--- a/drivers/net/wireless/intersil/p54/p54.h
+++ b/drivers/net/wireless/intersil/p54/p54.h
@@ -126,7 +126,7 @@ struct p54_cal_database {
size_t entry_size;
size_t offset;
size_t len;
- u8 data[];
+ u8 data[] __counted_by(entries);
This looks incorrect - I think you want __counted_by(len)? The
I think you're right. More comments below...
presence of entry_size made me suspicious.
};
This is the function that creates struct p54_cal_database:
static struct p54_cal_database *p54_convert_db(struct pda_custom_wrapper *src,
size_t total_len)
{
struct p54_cal_database *dst;
size_t payload_len, entries, entry_size, offset;
payload_len = le16_to_cpu(src->len);
entries = le16_to_cpu(src->entries);
entry_size = le16_to_cpu(src->entry_size);
offset = le16_to_cpu(src->offset);
if (((entries * entry_size + offset) != payload_len) ||
(payload_len + sizeof(*src) != total_len))
return NULL;
dst = kmalloc(sizeof(*dst) + payload_len, GFP_KERNEL);
if (!dst)
return NULL;
dst->entries = entries;
dst->entry_size = entry_size;
dst->offset = offset;
dst->len = payload_len;
memcpy(dst->data, src->data, payload_len);
return dst;
}
You can see that kmalloc is performed with `sizeof(*dst) +
payload_len`, and payload_len is assigned to ->len.
This should be changed to:
- dst = kmalloc(sizeof(*dst) + payload_len, GFP_KERNEL);
+ dst = kmalloc(struct_size(dst, data, payload_len), GFP_KERNEL);
I don't read Coccinelle, but, if this patch was auto-generated, I
wonder if the script has an error.
With the struct_size() change, the Coccinelle script should be able to
generate a correct patch for this.
--
Gustavo
