linux-kernel - [PATCH] wireless: mwifiex: fix double free

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Date:   Sun,  4 Oct 2020 06:19:31 -0700
From:   trix@...hat.com
To:     amitkarwar@...il.com, ganapathi.bhat@....com,
        huxinming820@...il.com, kvalo@...eaurora.org, davem@...emloft.net,
        kuba@...nel.org, natechancellor@...il.com, ndesaulniers@...gle.com,
        linville@...driver.com, nishants@...vell.com, rramesh@...vell.com,
        bzhao@...vell.com, frankh@...vell.com
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] wireless: mwifiex: fix double free

From: Tom Rix <trix@...hat.com>

clang static analysis reports this problem:

sdio.c:2403:3: warning: Attempt to free released memory
        kfree(card->mpa_rx.buf);
        ^~~~~~~~~~~~~~~~~~~~~~~

When mwifiex_init_sdio() fails in its first call to
mwifiex_alloc_sdio_mpa_buffer, it falls back to calling it
again.  If the second alloc of mpa_tx.buf fails, the error
handler will try to free the old, previously freed mpa_rx.buf.
Reviewing the code, it looks like a second double free would
happen with mwifiex_cleanup_sdio().

So set both pointers to NULL when they are freed.

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/net/wireless/marvell/mwifiex/sdio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/wireless/marvell/mwifiex/sdio.c b/drivers/net/wireless/marvell/mwifiex/sdio.c
index 69911c728eb1..bde9e4bbfffe 100644
--- a/drivers/net/wireless/marvell/mwifiex/sdio.c
+++ b/drivers/net/wireless/marvell/mwifiex/sdio.c
@@ -2403,6 +2403,8 @@ static int mwifiex_alloc_sdio_mpa_buffers(struct mwifiex_adapter *adapter,
 		kfree(card->mpa_rx.buf);
 		card->mpa_tx.buf_size = 0;
 		card->mpa_rx.buf_size = 0;
+		card->mpa_tx.buf = NULL;
+		card->mpa_rx.buf = NULL;
 	}
 
 	return ret;
-- 
2.18.1