ixgbe: ethtool: stats user buffer overrun
If the number of tx/rx queues changes the ethtool ioctl ETHTOOL_GSTATS may overrun the userspace buffer. This occurs because the general practice in user space to query stats is to issue a ETHTOOL_GSSET cmd to learn the buffer size needed, allocate the buffer, then call ETHTOOL_GSTIRNGS and ETHTOOL_GSTATS. If the number of real_num_queues is changed or flow control attributes are changed after ETHTOOL_GSSET but before the ETHTOOL_GSTRINGS/ETHTOOL_GSTATS a user space buffer overrun occurs. To fix the overrun always return the max buffer size needed from get_sset_count() then return all strings and stats from get_strings()/get_ethtool_stats(). This _will_ change the output from the ioctl() call which could break applications and script parsing in theory. I believe these changes should not break existing tools because the only changes will be more {tx|rx}_queues and the {tx|rx}_pb_* stats will always be returned. Existing scripts already need to handle changing number of queues because this occurs today depending on system and current features. The {tx|rx}_pb_* stats are at the end of the output and should be handled by scripts today regardless. Finally get_ethtool_stats and get_strings are free-form outputs tools parsing these outputs should be defensive anyways. In the end these updates are better then having a tool segfault because of a buffer overrun. Signed-off-by:John Fastabend <john.r.fastabend@intel.com> Signed-off-by:
Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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