Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

ice: fix Rx page leak on multi-buffer frames

The ice_put_rx_mbuf() function handles calling ice_put_rx_buf() for each buffer in the current frame. This function was introduced as part of handling multi-buffer XDP support in the ice driver.

It works by iterating over the buffers from first_desc up to 1 plus the total number of fragments in the frame, cached from before the XDP program was executed.

If the hardware posts a descriptor with a size of 0, the logic used in ice_put_rx_mbuf() breaks. Such descriptors get skipped and don't get added as fragments in ice_add_xdp_frag. Since the buffer isn't counted as a fragment, we do not iterate over it in ice_put_rx_mbuf(), and thus we don't call ice_put_rx_buf().

Because we don't call ice_put_rx_buf(), we don't attempt to re-use the page or free it. This leaves a stale page in the ring, as we don't increment next_to_alloc.

The ice_reuse_rx_page() assumes that the next_to_alloc has been incremented properly, and that it always points to a buffer with a NULL page. Since this function doesn't check, it will happily recycle a page over the top of the next_to_alloc buffer, losing track of the old page.

Note that this leak only occurs for multi-buffer frames. The ice_put_rx_mbuf() function always handles at least one buffer, so a single-buffer frame will always get handled correctly. It is not clear precisely why the hardware hands us descriptors with a size of 0…