[PATCH AUTOSEL 6.6 01/62] net: macb: Check return value of dma_set_mask_and_coherent()

[Sasha Levin <sashal@kernel.org>]

From: Sergio Perez Gonzalez <sperezglz@gmail.com>

[ Upstream commit 3920a758800762917177a6b5ab39707d8e376fe6 ]

Issue flagged by coverity. Add a safety check for the return value
of dma_set_mask_and_coherent, go to a safe exit if it returns error.

Link: https://scan7.scan.coverity.com/#/project-view/53936/11354?selectedIssue=1643754
Signed-off-by: Sergio Perez Gonzalez <sperezglz@gmail.com>
Reviewed-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Link: https://patch.msgid.link/20250526032034.84900-1-sperezglz@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

Based on my analysis of the commit and the codebase context, here's my
assessment: **YES** This commit should be backported to stable kernel
trees. Here's my extensive analysis: ## Code Analysis The commit adds
proper error checking for `dma_set_mask_and_coherent()` in the macb
network driver. Looking at the specific changes: **Before the fix:**
```c if (GEM_BFEXT(DAW64, gem_readl(bp, DCFG6))) {
dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(44)); bp->hw_dma_cap
|= HW_DMA_CAP_64B; } ``` **After the fix:** ```c if (GEM_BFEXT(DAW64,
gem_readl(bp, DCFG6))) { err = dma_set_mask_and_coherent(&pdev->dev,
DMA_BIT_MASK(44)); if (err) { dev_err(&pdev->dev, "failed to set DMA
mask\n"); goto err_out_free_netdev; } bp->hw_dma_cap |= HW_DMA_CAP_64B;
} ``` ## Why this should be backported: 1. **Fixes a Real Bug**: The
original code ignores the return value of `dma_set_mask_and_coherent()`.
If this function fails (which can happen on systems with restricted DMA
capabilities), the driver would continue execution assuming 44-bit DMA
addressing is available when it's not, leading to potential memory
corruption or system crashes. 2. **Small, Contained Fix**: This is a
minimal change that only adds proper error checking without changing any
core logic or introducing new features. It follows the stable tree
principle of being a small, targeted bugfix. 3. **Follows Established
Patterns**: Looking at the similar commits provided, this matches
exactly the pattern of commits marked "YES" for backporting (commits #1,
#2, and #5) which all add proper error checking for DMA mask functions.
4. **Critical Network Driver**: The macb driver is used in production
systems, and DMA-related bugs can cause data corruption or system
instability, making this a high-priority fix for stable trees. 5.
**Proper Error Handling Path**: The fix correctly uses the existing
`err_out_free_netdev` label, which properly cleans up allocated
resources (line 5373-5383 in macb_main.c), preventing resource leaks
when DMA setup fails. 6. **Static Analysis Tool Flagged**: The commit
message mentions this was flagged by Coverity, indicating it's a
legitimate code quality issue that could manifest as a runtime bug. 7.
**Matches Stable Tree Criteria**: - Important bugfix ✓ - Minimal risk of
regression ✓ - No architectural changes ✓ - Confined to one
driver/subsystem ✓ - Clear side effects (proper cleanup on failure) ✓
This commit addresses the same class of vulnerability as the other "YES"
examples: ignoring return values of critical DMA functions that can fail
and lead to undefined behavior. The fix is surgical, safe, and addresses
a genuine runtime issue in a widely-used network driver.

 drivers/net/ethernet/cadence/macb_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 6f45f4d9fba71..534e7f7bca4c2 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -5070,7 +5070,11 @@ static int macb_probe(struct platform_device *pdev)
 
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
 	if (GEM_BFEXT(DAW64, gem_readl(bp, DCFG6))) {
-		dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(44));
+		err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(44));
+		if (err) {
+			dev_err(&pdev->dev, "failed to set DMA mask\n");
+			goto err_out_free_netdev;
+		}
 		bp->hw_dma_cap |= HW_DMA_CAP_64B;
 	}
 #endif
-- 
2.39.5