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=164... 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 667af80a739b9..2266a3ecc5533 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -4809,7 +4809,11 @@ 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