Re: [PATCH] smb: server: fix max_connections off-by-one in tcp accept path

[Namjae Jeon]

On Fri, Apr 17, 2026 at 6:17 AM DaeMyung Kang <charsyam@xxxxxxxxx> wrote:
>
> The global max_connections check in ksmbd's TCP accept path counts
> the newly accepted connection with atomic_inc_return(), but then
> rejects the connection when the result is greater than or equal to
> server_conf.max_connections.
>
> That makes the effective limit one smaller than configured. For
> example:
>
> - max_connections=1 rejects the first connection
> - max_connections=2 allows only one connection
>
> The per-IP limit in the same function uses <= correctly because it
> counts only pre-existing connections. The global limit instead checks
> the post-increment total, so it should reject only when that total
> exceeds the configured maximum.
>
> Fix this by changing the comparison from >= to >, so exactly
> max_connections simultaneous connections are allowed and the next one
> is rejected. This matches the documented meaning of max_connections
> in fs/smb/server/ksmbd_netlink.h as the "Number of maximum simultaneous
> connections".
>
> Fixes: 0d0d4680db22 ("ksmbd: add max connections parameter")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: DaeMyung Kang <charsyam@xxxxxxxxx>
Applied it to #ksmbd-for-next-next.
Thanks!