[PATCH] net: mvneta: fix double free of txq->buf

[PATCH] net: mvneta: fix double free of txq->buf

[trix]

From: Tom Rix <trix@redhat.com>

clang static analysis reports this problem:

drivers/net/ethernet/marvell/mvneta.c:3465:2: warning:
  Attempt to free released memory
        kfree(txq->buf);
        ^~~~~~~~~~~~~~~

When mvneta_txq_sw_init() fails to alloc txq->tso_hdrs,
it frees without poisoning txq->buf.  The error is caught
in the mvneta_setup_txqs() caller which handles the error
by cleaning up all of the txqs with a call to
mvneta_txq_sw_deinit which also frees txq->buf.

Since mvneta_txq_sw_deinit is a general cleaner, all of the
partial cleaning in mvneta_txq_sw_deinit()'s error handling
is not needed.

Fixes: 2adb719d74f6 ("net: mvneta: Implement software TSO")
Signed-off-by: Tom Rix <trix@redhat.com>
---
 drivers/net/ethernet/marvell/mvneta.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index d095718355d3..54b0bf574c05 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -3397,24 +3397,15 @@ static int mvneta_txq_sw_init(struct mvneta_port *pp,
 	txq->last_desc = txq->size - 1;
 
 	txq->buf = kmalloc_array(txq->size, sizeof(*txq->buf), GFP_KERNEL);
-	if (!txq->buf) {
-		dma_free_coherent(pp->dev->dev.parent,
-				  txq->size * MVNETA_DESC_ALIGNED_SIZE,
-				  txq->descs, txq->descs_phys);
+	if (!txq->buf)
 		return -ENOMEM;
-	}
 
 	/* Allocate DMA buffers for TSO MAC/IP/TCP headers */
 	txq->tso_hdrs = dma_alloc_coherent(pp->dev->dev.parent,
 					   txq->size * TSO_HEADER_SIZE,
 					   &txq->tso_hdrs_phys, GFP_KERNEL);
-	if (!txq->tso_hdrs) {
-		kfree(txq->buf);
-		dma_free_coherent(pp->dev->dev.parent,
-				  txq->size * MVNETA_DESC_ALIGNED_SIZE,
-				  txq->descs, txq->descs_phys);
+	if (!txq->tso_hdrs)
 		return -ENOMEM;
-	}
 
 	/* Setup XPS mapping */
 	if (txq_number > 1)
-- 
2.18.1

Re: [PATCH] net: mvneta: fix double free of txq->buf

[David Miller]

From: trix@redhat.com
Date: Sat,  3 Oct 2020 11:51:21 -0700

> From: Tom Rix <trix@redhat.com>
> 
> clang static analysis reports this problem:
> 
> drivers/net/ethernet/marvell/mvneta.c:3465:2: warning:
>   Attempt to free released memory
>         kfree(txq->buf);
>         ^~~~~~~~~~~~~~~
> 
> When mvneta_txq_sw_init() fails to alloc txq->tso_hdrs,
> it frees without poisoning txq->buf.  The error is caught
> in the mvneta_setup_txqs() caller which handles the error
> by cleaning up all of the txqs with a call to
> mvneta_txq_sw_deinit which also frees txq->buf.
> 
> Since mvneta_txq_sw_deinit is a general cleaner, all of the
> partial cleaning in mvneta_txq_sw_deinit()'s error handling
> is not needed.
> 
> Fixes: 2adb719d74f6 ("net: mvneta: Implement software TSO")
> Signed-off-by: Tom Rix <trix@redhat.com>

Applied and queued up for -stable, thank you.