[PATCH] net: qrtr: fix 32-bit integer overflow in qrtr_endpoint_post()

[Michael Bommarito <michael.bommarito@gmail.com>]

qrtr_endpoint_post() validates an incoming packet with

	if (!size || len != ALIGN(size, 4) + hdrlen)
		goto err;

where size comes from the wire. On 32-bit, size_t is 32 bits and
ALIGN(size, 4) wraps to 0 for size >= 0xfffffffd, so the check
passes and skb_put_data(skb, data + hdrlen, size) writes past the
hdrlen-sized skb and oopses the kernel. 64-bit is unaffected.

This is the 32-bit residual of ad9d24c9429e2 ("net: qrtr: fix OOB
Read in qrtr_endpoint_post"), which fixed only the 64-bit case.

Reject any size that cannot fit the buffer before the ALIGN.

Fixes: ad9d24c9429e2 ("net: qrtr: fix OOB Read in qrtr_endpoint_post")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
---
32-bit only; reachable via /dev/qrtr-tun (CONFIG_QRTR_TUN) or a QMI modem.
Reproduced on i386 (a 32-byte write with size 0xfffffffd faults; well-formed
writes are unaffected).  QRTR mostly runs on 64-bit now, so this is a
correctness fix completing ad9d24c9429e2, not a high-severity bug.

 net/qrtr/af_qrtr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index 7cec6a7859b03..ba6d38244c440 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -496,7 +496,7 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
 	if (cb->dst_port == QRTR_PORT_CTRL_LEGACY)
 		cb->dst_port = QRTR_PORT_CTRL;
 
-	if (!size || len != ALIGN(size, 4) + hdrlen)
+	if (!size || size > len || len != ALIGN(size, 4) + hdrlen)
 		goto err;
 
 	if ((cb->type == QRTR_TYPE_NEW_SERVER ||

base-commit: 5200f5f493f79f14bbdc349e402a40dfb32f23c8
-- 
2.53.0