Re: [PATCH net] dibs: loopback: validate offset and size in move_data()

[Dust Li]

On 2026-07-07 15:43:18, Dust Li wrote:
>The loopback move_data() performs a memcpy into the registered DMB
>without checking whether offset + size exceeds the DMB length.  Unlike
>real ISM hardware, which enforces memory region bounds natively, the
>software loopback has no such protection.
>
>A peer-supplied out-of-bounds offset or oversized write would result in
>an OOB write past the allocated kernel buffer.  Add an explicit bounds
>check before the memcpy to reject such requests with -EINVAL.
>
>Fixes: f7a22071dbf3("net/smc: implement DMB-related operations of loopback-ism")
>Cc: stable@xxxxxxxxxxxxxxx
>Reported-by: Federico Kirschbaum <federico.kirschbaum@xxxxxxxx>

Reported-by: Baul Lee <baul.lee@xxxxxxxx>

Best regards,
Dust

>Signed-off-by: Dust Li <dust.li@xxxxxxxxxxxxxxxxx>
>---
> drivers/dibs/dibs_loopback.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
>diff --git a/drivers/dibs/dibs_loopback.c b/drivers/dibs/dibs_loopback.c
>index ec3b48cb0e87..0f2e09311152 100644
>--- a/drivers/dibs/dibs_loopback.c
>+++ b/drivers/dibs/dibs_loopback.c
>@@ -254,6 +254,11 @@ static int dibs_lo_move_data(struct dibs_dev *dibs, u64 dmb_tok,
> 		read_unlock_bh(&ldev->dmb_ht_lock);
> 		return -EINVAL;
> 	}
>+	if ((u64)offset + size > rmb_node->len) {
>+		read_unlock_bh(&ldev->dmb_ht_lock);
>+		return -EINVAL;
>+	}
>+
> 	memcpy((char *)rmb_node->cpu_addr + offset, data, size);
> 	sba_idx = rmb_node->sba_idx;
> 	read_unlock_bh(&ldev->dmb_ht_lock);
>-- 
>2.43.7