On Wed, Jun 15, 2022 at 10:29:24PM -0500, Martin Faltesek wrote:
commit f2e19b36593caed4c977c2f55aeba7408aeb2132 upstream.
The transaction buffer is allocated by using the size of the packet buf, and subtracting two which seem intended to remove the two tags which are not present in the target structure. This calculation leads to under counting memory because of differences between the packet contents and the target structure. The aid_len field is a u8 in the packet, but a u32 in the structure, resulting in at least 3 bytes always being under counted. Further, the aid data is a variable length field in the packet, but fixed in the structure, so if this field is less than the max, the difference is added to the under counting.
The last validation check for transaction->params_len is also incorrect since it employs the same accounting error.
To fix, perform validation checks progressively to safely reach the next field, to determine the size of both buffers and verify both tags. Once all validation checks pass, allocate the buffer and copy the data. This eliminates freeing memory on the error path, as those checks are moved ahead of memory allocation.
Fixes: 26fc6c7f02cb ("NFC: st21nfca: Add HCI transaction event support") Fixes: 4fbcc1a4cb20 ("nfc: st21nfca: Fix potential buffer overflows in EVT_TRANSACTION") Cc: stable@vger.kernel.org Signed-off-by: Martin Faltesek mfaltesek@google.com Reviewed-by: Guenter Roeck groeck@chromium.org Reviewed-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Signed-off-by: Jakub Kicinski kuba@kernel.org Change-Id: I22f9d58293b64566c43a7ba254d9e0e8c4dc35fe
change-id makes no sense for kernel work, sorry.
I'll delete it...