ACK+CMNT: [PATCH 0/1][SRU][FOCAL][GROOVY] tcp: correct read of TFO keys on big endian systems

[Thadeu Lima de Souza Cascardo]

On Tue, Aug 11, 2020 at 05:01:39PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1869134
> 
> == SRU Justification Focal, Groovy ==
> 
> Running the tcp_fastopen_backup_key.sh from net in ubuntu_kernel_selftests
> fails on little endian systems. This is a regression that occurred because

You mean they fail on big endian systems, right?

The fact that there is no clear bounds checking in that code makes me a little
uneasy, but I don't see regressions on this patch on that regard. And by
inspecting the code, tcp_fastopen_context_len will return the value for a
member that is initialized to either 1 or 2 right after allocation. And
TCP_FASTOPEN_KEY_MAX is 2.

But worse yet is all these shenanigans with types. Is it a u32, a u64 or a
siphash_key_t? Is it decided yet? But it seems this is just fine too, as all
buffers are sized TCP_FASTOPEN_KEY_BUF_LENGTH.

The test seem to be specific to the sysctl interface. Or is getsockopt tested
at all?

Acked-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>

> of commit 438ac88009bc ("net: fastopen: robustness and endianness fixes
> for SipHash"). 
> 
> == Fix ==
> 
> Upstream (linux-next) fix:
> 
>   commit f19008e676366c44e9241af57f331b6c6edf9552
>   Author: Jason Baron <jbaron at akamai.com>
>   Date:   Mon Aug 10 13:38:39 2020 -0400
> 
>       tcp: correct read of TFO keys on big endian systems
> 
> == Test case ==
> 
> Run the kernel self tests tcp_fastopen_backup_key.sh.  Currently this fails
> on the last few test cases.  With the fix the test passes.
> 
> == Regression Potential == 
> 
> This fix touches the tcp fast open code paths so it can potentially impact
> TCP fast opening and perhaps the TCP opening. However, this has been tested
> on big and little endian systems with the regression tests, so the
> regression risk is low with this fix.
> 
> -----
> 
> Jason Baron (1):
>   tcp: correct read of TFO keys on big endian systems
> 
>  include/net/tcp.h          |  2 ++
>  net/ipv4/sysctl_net_ipv4.c | 16 ++++------------
>  net/ipv4/tcp.c             | 16 ++++------------
>  net/ipv4/tcp_fastopen.c    | 23 +++++++++++++++++++++++
>  4 files changed, 33 insertions(+), 24 deletions(-)
> 
> -- 
> 2.27.0
> 
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team