FAILED: patch "[PATCH] dibs: loopback: validate offset and size in move_data()" failed to apply to 6.12-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 78237e3c0720fcc6eb9b87e90fd70f63eeca886f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026072130-tadpole-coauthor-d48e@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 78237e3c0720fcc6eb9b87e90fd70f63eeca886f Mon Sep 17 00:00:00 2001
From: Dust Li <dust.li@linux.alibaba.com>
Date: Tue, 7 Jul 2026 15:43:18 +0800
Subject: [PATCH] dibs: loopback: validate offset and size in move_data()

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@vger.kernel.org
Reported-by: Federico Kirschbaum <federico.kirschbaum@xbow.com>
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Reported-by: Baul Lee <baul.lee@xbow.com>
Link: https://patch.msgid.link/20260707074318.1448662-1-dust.li@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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);