igb: cope with large MAX_SKB_FRAGS

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: igb: cope with large MAX_SKB_FRAGS Sabrina reports that the igb driver does not cope well with large MAX_SKB_FRAG values: setting MAX_SKB_FRAG to 45 causes payload corruption on TX. An easy reproducer is to run ssh to connect to the machine. With MAX_SKB_FRAGS=17 it works, with MAX_SKB_FRAGS=45 it fails. This has been reported originally in https://bugzilla.redhat.com/show_bug.cgi?id=2265320 The root cause of the issue is that the driver does not take into account properly the (possibly large) shared info size when selecting the ring layout, and will try to fit two packets inside the same 4K page even when the 1st fraglist will trump over the 2nd head. Address the issue by checking if 2K buffers are insufficient.

References

• https://git.kernel.org/stable/c/8ea80ff5d8298356d28077bc30913ed37df65109
• https://git.kernel.org/stable/c/b52bd8bcb9e8ff250c79b44f9af8b15cae8911ab
• https://git.kernel.org/stable/c/8aba27c4a5020abdf60149239198297f88338a8d