Re: [PATCH 1/2] ocfs2/dlm: validate qr_numregions in dlm_match_regions()

[Joseph Qi <joseph.qi@linux.alibaba.com>]

On 3/7/26 3:21 PM, Junrui Luo wrote:
> The qr_numregions field from a DLM_QUERY_REGION network message is used
> directly as loop bounds in dlm_match_regions() without checking against
> O2NM_MAX_REGIONS. Since qr_regions is sized for at most O2NM_MAX_REGIONS
> (32) entries, a crafted message with qr_numregions > 32 causes
> out-of-bounds reads past the qr_regions buffer.
> 
> Add a bounds check for qr_numregions before entering the loops.
> 
> Fixes: ea2034416b54 ("ocfs2/dlm: Add message DLM_QUERY_REGION")
> Reported-by: Yuhao Jiang <danisjiang@gmail.com>
> Signed-off-by: Junrui Luo <moonafterrain@outlook.com>

Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>

> ---
>  fs/ocfs2/dlm/dlmdomain.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
> index 70ca79e4bdc3..0a28cb5ded2a 100644
> --- a/fs/ocfs2/dlm/dlmdomain.c
> +++ b/fs/ocfs2/dlm/dlmdomain.c
> @@ -980,6 +980,14 @@ static int dlm_match_regions(struct dlm_ctxt *dlm,
>  		goto bail;
>  	}
>  
> +	if (qr->qr_numregions > O2NM_MAX_REGIONS) {
> +		mlog(ML_ERROR, "Domain %s: Joining node %d has invalid "
> +		     "number of heartbeat regions %u\n",
> +		     qr->qr_domain, qr->qr_node, qr->qr_numregions);
> +		status = -EINVAL;
> +		goto bail;
> +	}
> +
>  	r = remote;
>  	for (i = 0; i < qr->qr_numregions; ++i) {
>  		mlog(0, "Region %.*s\n", O2HB_MAX_REGION_NAME_LEN, r);
>