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From: Marc Kleine-Budde <mkl@pengutronix.de>
To: coverity-bot <keescook@chromium.org>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	linux-next@vger.kernel.org, linux-can <linux-can@vger.kernel.org>
Subject: Re: Coverity: mcp251xfd_dump_rx_ring(): Memory - illegal accesses
Date: Thu, 1 Apr 2021 09:49:04 +0200
Message-ID: <20210401074904.ucgl4pictqaw6gew@pengutronix.de> (raw)
In-Reply-To: <202103311459.93EB7DEBDC@keescook>


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On 31.03.2021 14:59:44, coverity-bot wrote:
> This is an experimental semi-automated report about issues detected by
> Coverity from a scan of next-20210331 as part of the linux-next scan project:
> https://scan.coverity.com/projects/linux-next-weekly-scan
> 
> You're getting this email because you were associated with the identified
> lines of code (noted below) that were touched by commits:
> 
>   None
>     e0ab3dd5f98f ("can: mcp251xfd: add dev coredump support")
> 
> Coverity reported the following:
> 
> *** CID 1503585:  Memory - illegal accesses  (OVERRUN)
> /drivers/net/can/spi/mcp251xfd/mcp251xfd-dump.c: 190 in mcp251xfd_dump_rx_ring()
> 184     static void mcp251xfd_dump_rx_ring(const struct mcp251xfd_priv *priv,
> 185     				   struct mcp251xfd_dump_iter *iter)
> 186     {
> 187     	struct mcp251xfd_rx_ring *rx_ring;
> 188     	unsigned int i;
> 189
> vvv     CID 1503585:  Memory - illegal accesses  (OVERRUN)
> vvv     Overrunning array of 1 8-byte elements at element index 1 (byte offset 15) by dereferencing pointer "priv->rx + i".
> 190     	mcp251xfd_for_each_rx_ring(priv, rx_ring, i)
> 191     		mcp251xfd_dump_rx_ring_one(priv, iter, rx_ring);

mcp251xfd_for_each_rx_ring is a macro that iterates over all RX rings in
the struct mcp251xfd_priv. It's not pretty (as it uses its arguments
more than once), but it works:

| #define mcp251xfd_for_each_rx_ring(priv, ring, n) \
| 	for ((n) = 0, (ring) = *((priv)->rx + (n)); \
| 	     (n) < (priv)->rx_ring_num; \
| 	     (n)++, (ring) = *((priv)->rx + (n)))

For now there is only one rx ring...

| struct mcp251xfd_priv {
|       [...]
| 	struct mcp251xfd_rx_ring *rx[1];
| 	u8 rx_ring_num;
|       [...]
| }

...and rx_ring_num is initialized as "1".

| 	for (i = 0;
| 	     i < ARRAY_SIZE(priv->rx) && ram_free >= rx_obj_size;
| 	     i++) {
|               [...]
| 	}
| 	priv->rx_ring_num = i;


> 192     }
> 193
> 194     static void mcp251xfd_dump_tx_ring(const struct mcp251xfd_priv *priv,
> 195     				   struct mcp251xfd_dump_iter *iter)
> 
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):

This looks indeed like a false positive to me.

> Reported-by: coverity-bot <keescook+coverity-bot@chromium.org>
> Addresses-Coverity-ID: 1503585 ("Memory - illegal accesses")
> Fixes: e0ab3dd5f98f ("can: mcp251xfd: add dev coredump support")

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-31 21:59 coverity-bot
2021-04-01  7:49 ` Marc Kleine-Budde [this message]
2021-04-01 20:37   ` Kees Cook

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