[PATCH v2 1/2] wifi: brcmfmac: make release_scratchbuffers idempotent

[Fan Wu]

brcmf_pcie_release_scratchbuffers() frees the shared.scratch and
shared.ringupd DMA buffers with dma_free_coherent() but does not clear
the pointers afterwards, unlike the sibling release_ringbuffers() which
NULLs commonrings/flowrings/idxbuf on release.

Both the bus_reset .reset callback (brcmf_pcie_reset) and
brcmf_pcie_remove() call release_scratchbuffers.  When reset teardown
has run before removal, remove's own teardown would call
dma_free_coherent() a second time on the already-freed DMA allocation.

NULL the pointers after free, matching release_ringbuffers(), so a later
release observes that the allocation has already been released.  This
patch makes repeated sequential release safe; the reset-work lifetime is
handled separately by the following patch.

This issue was found by an in-house static analysis tool.

Fixes: 4684997d9eea ("brcmfmac: reset PCIe bus on a firmware crash")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Fan Wu <fanwu01@xxxxxxxxxx>
Assisted-by: Codex:gpt-5.6
---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
index 13662aa4b..9f10b3fff 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
@@ -1383,16 +1383,20 @@ static int brcmf_pcie_init_ringbuffers(struct brcmf_pciedev_info *devinfo)
 static void
 brcmf_pcie_release_scratchbuffers(struct brcmf_pciedev_info *devinfo)
 {
-	if (devinfo->shared.scratch)
+	if (devinfo->shared.scratch) {
 		dma_free_coherent(&devinfo->pdev->dev,
 				  BRCMF_DMA_D2H_SCRATCH_BUF_LEN,
 				  devinfo->shared.scratch,
 				  devinfo->shared.scratch_dmahandle);
-	if (devinfo->shared.ringupd)
+		devinfo->shared.scratch = NULL;
+	}
+	if (devinfo->shared.ringupd) {
 		dma_free_coherent(&devinfo->pdev->dev,
 				  BRCMF_DMA_D2H_RINGUPD_BUF_LEN,
 				  devinfo->shared.ringupd,
 				  devinfo->shared.ringupd_dmahandle);
+		devinfo->shared.ringupd = NULL;
+	}
 }
 
 static int brcmf_pcie_init_scratchbuffers(struct brcmf_pciedev_info *devinfo)
-- 
2.34.1