[PATCH] wireless: mwifiex: fix double free

[PATCH] wireless: mwifiex: fix double free

[trix]

From: Tom Rix <trix@redhat.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@redhat.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

Re: [PATCH] wireless: mwifiex: fix double free

[Brian Norris]

On Sun, Oct 4, 2020 at 6:19 AM <trix@redhat.com> wrote:
>
> From: Tom Rix <trix@redhat.com>
>
> clang static analysis reports this problem:
>
> sdio.c:2403:3: warning: Attempt to free released memory
>         kfree(card->mpa_rx.buf);
>         ^~~~~~~~~~~~~~~~~~~~~~~

That's some interesting static analysis for a compiler.

> 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@redhat.com>

For whatever it's worth:

Reviewed-by: Brian Norris <briannorris@chromium.org>

Re: mwifiex: fix double free

[Kalle Valo]

trix@redhat.com wrote:

> From: Tom Rix <trix@redhat.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@redhat.com>
> Reviewed-by: Brian Norris <briannorris@chromium.org>

Patch applied to wireless-drivers-next.git, thanks.

53708f4fd9cf mwifiex: fix double free

-- 
https://patchwork.kernel.org/patch/11815655/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches