CVE-2021-46935

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> binder: fix async_free_space accounting for empty parcels<br /> <br /> In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space")<br /> fixed a kernel structure visibility issue. As part of that patch,<br /> sizeof(void *) was used as the buffer size for 0-length data payloads so<br /> the driver could detect abusive clients sending 0-length asynchronous<br /> transactions to a server by enforcing limits on async_free_size.<br /> <br /> Unfortunately, on the "free" side, the accounting of async_free_space<br /> did not add the sizeof(void *) back. The result was that up to 8-bytes of<br /> async_free_space were leaked on every async transaction of 8-bytes or<br /> less. These small transactions are uncommon, so this accounting issue<br /> has gone undetected for several years.<br /> <br /> The fix is to use "buffer_size" (the allocated buffer size) instead of<br /> "size" (the logical buffer size) when updating the async_free_space<br /> during the free operation. These are the same except for this<br /> corner case of asynchronous transactions with payloads