Coverity: mcp251xfd_dump_rx_ring(): Memory - illegal accesses

DISCUSSION coverity-bot 2 participants 3 messages Mar 31, 2021 – Apr 1, 2021

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Linux-next tree CAN network drivers

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coverity-bot

author

2021-03-31 22:00 UTC #0 lore raw

Hello!

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);
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):

Reported-by coverity-bot <[email protected]>

Addresses-Coverity-ID: 1503585 ("Memory - illegal accesses")

Fixes e0ab3dd5f98f ("can: mcp251xfd: add dev coredump support")

Thanks for your attention!

Signature · 1 line

Coverity-bot

Marc Kleine-Budde

maintainer

2021-04-01 07:49 UTC #1 lore raw

Quoted 14 lines · coverity-bot

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()

Quoted 10 lines

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;

Quoted 9 lines

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.

Quoted 3 lines

Reported-by coverity-bot <[email protected]>
Addresses-Coverity-ID: 1503585 ("Memory - illegal accesses")
Fixes e0ab3dd5f98f ("can: mcp251xfd: add dev coredump support")

regards,
Marc

Signature · 4 lines

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 |

Kees Cook

author

2021-04-01 20:37 UTC #2 lore raw

Quoted 26 lines · Marc Kleine-Budde

Quoted 14 lines · coverity-bot
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()
Quoted 10 lines
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);

Quoted 3 lines

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:

Ah yes; thanks! This is another "for each" macro that that confuses Coverity. I'll try to silence these...

Thanks for the details and taking a look at it!

-Kees

Quoted 49 lines

| #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;
Quoted 9 lines
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.
Quoted 3 lines
Reported-by coverity-bot <[email protected]>
Addresses-Coverity-ID: 1503585 ("Memory - illegal accesses")
Fixes e0ab3dd5f98f ("can: mcp251xfd: add dev coredump support")
regards,
Marc
Signature · 4 lines
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 |

Signature · 1 line

Kees Cook