In the Linux kernel, the following vulnerability has been resolved:
esp: fix page frag reference leak on skb_to_sgvec failure
In esp_output_tail(), when esp->inplace is false, the old skb page frags are replaced with a new page from the xfrm page_frag cache. The source scatterlist (sg) is built from the old frags before the replacement, and esp_ssg_unref() is responsible for releasing the old page references after the crypto operation completes.
However, if the second skb_to_sgvec() call (which builds the destination scatterlist from the new page) fails, the code jumps to error_free which only calls kfree(tmp). The old page frag references captured in the source scatterlist are never released:
- sg[] is built from old frags via skb_to_sgvec() (no extra get_page)
- nr_frags is set to 1 and frag[0] is replaced with the new page
- Second skb_to_sgvec() fails -> goto error_free
- kfree(tmp) frees the sg[] memory but old frags are not unref'd
- kfree_skb() only releases frag[0] (the new page), not the old ones
Fix this by adding a bool parameter to esp_ssg_unref() that, when true, unconditionally unrefs the source scatterlist frags without checking req->src and req->dst, since those fields are not yet initialized by aead_request_set_crypt() at the point of the error. Existing callers pass false to preserve the original behavior.
The same issue exists in both esp4 and esp6 as the code is identical.