openwrt/target/linux/bcm27xx/patches-6.6/950-1047-dw-axi-dmac-platform-Avoid-trampling-with-zero-lengt.patch

From 5b3c219b5e5bc4ecd4e0dde7688929ff14cd08b0 Mon Sep 17 00:00:00 2001
From: popcornmix <popcornmix@gmail.com>
Date: Tue, 23 Apr 2024 09:51:36 +0100
Subject: [PATCH 1047/1085] dw-axi-dmac-platform: Avoid trampling with zero
 length buffer

This code:
for_each_sg(sgl, sg, sg_len, i)
  num_sgs += DIV_ROUND_UP(sg_dma_len(sg), axi_block_len);

determines how many hw_desc are allocated.
If sg_dma_len(sg)=0 we don't allocate for this sgl.

However in the next loop, we will increment loop
for this case, and loop gets higher than num_sgs
and we trample memory.

Signed-off-by: Dom Cobley <popcornmix@gmail.com>
---
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
+++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
@@ -834,6 +834,9 @@ dw_axi_dma_chan_prep_slave_sg(struct dma
 		mem = sg_dma_address(sg);
 		len = sg_dma_len(sg);
 		num_segments = DIV_ROUND_UP(sg_dma_len(sg), axi_block_len);
+		if (!num_segments)
+			continue;
+
 		segment_len = DIV_ROUND_UP(sg_dma_len(sg), num_segments);
 
 		do {