[PATCH net v4] net: stmmac: do not keep the new TSO MSS cached on mapping failures

[Linkui Xiao]

Hi,

Thanks for the reminder. Here is the missing information:

How discovered:
The original issue was found by code inspection of the error paths in
stmmac_tso_xmit(). The v3 regression - deferring tx_q->mss = mss until
the context descriptor OWN bit is set - was raised by the Sashiko AI
review of v3, which noted that a concurrent stmmac_tx_err() could reset
and clear tx_q->mss before the deferred store republished it. v4 avoids
that by keeping the store in place and clearing tx_q->mss on the DMA
mapping failure paths instead.

Triggered:
Not triggered on real hardware. This is a code-inspection/review finding.
The ring-wedge part requires a DMA mapping failure in the TSO transmit
path; the stale-MSS part then requires a later TSO frame with the same
gso_size to take the mss == tx_q->mss path and skip the context
descriptor. No stack trace, error message or syzbot report is available.

Testing:
Not tested on real hardware. No hardware test was performed.

On 2026/9/28 20:39, netdev-bot+sinfo at kernel.org wrote:
> Hi!
> 
> This is an automated message. This series looks like a fix, but its
> commit messages seem to be missing some information:
> 
>   - How the issue was discovered, e.g. hit in production, hit during
>     development, syzbot report, manual code inspection, LLM or static
>     analysis tool scan.
> 
>   - Whether the issue was actually triggered, or is only theoretical
>     (e.g. found by code inspection). If it was triggered please include
>     the symptoms, like the stack trace or error messages.
> 
>   - What hardware the change was tested on. For driver fixes please
>     mention the device (and if relevant firmware version) used for
>     testing, or say that the change was not tested on real hardware.
> 
> Please do not repost the series just to address the above. Instead,
> reply to this email with the missing information, so that reviewers
> can take it into account. If the series needs another revision for
> other reasons, please include the information in the commit messages
> then.
> 
> The evaluation is done by an LLM so it may be wrong, if you think
> that is the case please reply and explain.