Re: [PATCH net] netconsole: don't drop the last byte of a full-sized message

[Simon Horman]

On Tue, Jun 16, 2026 at 09:09:52AM -0700, Breno Leitao wrote:
> nt->buf is exactly MAX_PRINT_CHUNK bytes, but scnprintf() reserves one
> byte for its NUL terminator, so a non-fragmented payload of exactly
> MAX_PRINT_CHUNK loses its last byte (emitted as a stray NUL in the
> release path). Grow nt->buf to MAX_PRINT_CHUNK + 1 and bound the
> scnprintf() calls with sizeof(nt->buf); the transmitted length stays
> capped at MAX_PRINT_CHUNK.
> 
> Alternatively, nt->buf could be left at MAX_PRINT_CHUNK and the NUL byte
> reserved by routing exactly-MAX_PRINT_CHUNK payloads to fragmentation
> ('len < MAX_PRINT_CHUNK'), at the cost of fragmenting those messages.
> But it would look less sane, thus the current approach.
> 
> Fixes: c62c0a17f9b7 ("netconsole: Append kernel version to message")
> Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>