[PATCH v2] can: m_can: m_can_read_fifo: fix memory leak in error branch
From: Vincent Mailhol
Date: Sun Nov 07 2021 - 01:39:50 EST
In m_can_read_fifo(), if the second call to m_can_fifo_read() fails,
the function jump to the out_fail label and returns without calling
m_can_receive_skb(). This means that the skb previously allocated by
alloc_can_skb() is not freed. In other terms, this is a memory leak.
This patch adds a goto label to destroy the skb if an error occurs.
Issue was found with GCC -fanalyzer, please follow the link below for
details.
Fixes: e39381770ec9 ("can: m_can: Disable IRQs on FIFO bus errors")
CC: Matt Kline <matt@xxxxxxxxxxxxx>
Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
* Appendix: how the issue was found *
This issue was found using GCC's static analysis tool: -fanalyzer:
https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html
The step to reproduce are:
1. Install GCC 11.
2. Hack the kernel's Makefile to add the -fanalyzer flag (we leave
it as an exercise for the reader to figure out the details of how to
do so).
3. Decorate the function alloc_can_skb() with
__attribute__((__malloc__ (dealloc, netif_rx))). This step helps the
static analyzer to figure out the constructor/destructor pairs (not
something it can deduce by himself).
4. Compile.
The compiler then throws below warning:
| drivers/net/can/m_can/m_can.c: In function 'm_can_read_fifo':
| drivers/net/can/m_can/m_can.c:537:9: warning: leak of 'skb' [CWE-401] [-Wanalyzer-malloc-leak]
| 537 | return err;
| | ^~~~~~
| 'm_can_rx_handler': events 1-6
| |
| | 899 | static int m_can_rx_handler(struct net_device *dev, int quota)
| | | ^~~~~~~~~~~~~~~~
| | | |
| | | (1) entry to 'm_can_rx_handler'
| |......
| | 907 | if (!irqstatus)
| | | ~
| | | |
| | | (2) following 'false' branch (when 'irqstatus != 0')...
| |......
| | 920 | if (cdev->version <= 31 && irqstatus & IR_MRAF &&
| | | ~~
| | | |
| | | (3) ...to here
| |......
| | 939 | if (irqstatus & IR_RF0N) {
| | | ~
| | | |
| | | (4) following 'true' branch...
| | 940 | rx_work_or_err = m_can_do_rx_poll(dev, (quota - work_done));
| | | ~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | | | |
| | | | (6) calling 'm_can_do_rx_poll' from 'm_can_rx_handler'
| | | (5) ...to here
| |
| +--> 'm_can_do_rx_poll': events 7-8
| |
| | 540 | static int m_can_do_rx_poll(struct net_device *dev, int quota)
| | | ^~~~~~~~~~~~~~~~
| | | |
| | | (7) entry to 'm_can_do_rx_poll'
| |......
| | 548 | if (!(rxfs & RXFS_FFL_MASK)) {
| | | ~
| | | |
| | | (8) following 'false' branch...
| |
| 'm_can_do_rx_poll': event 9
| |
| |cc1:
| | (9): ...to here
| |
| 'm_can_do_rx_poll': events 10-12
| |
| | 553 | while ((rxfs & RXFS_FFL_MASK) && (quota > 0)) {
| | | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
| | | |
| | | (10) following 'true' branch...
| | 554 | err = m_can_read_fifo(dev, rxfs);
| | | ~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~
| | | | |
| | | | (12) calling 'm_can_read_fifo' from 'm_can_do_rx_poll'
| | | (11) ...to here
| |
| +--> 'm_can_read_fifo': events 13-24
| |
| | 470 | static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
| | | ^~~~~~~~~~~~~~~
| | | |
| | | (13) entry to 'm_can_read_fifo'
| |......
| | 484 | if (err)
| | | ~
| | | |
| | | (14) following 'false' branch...
| |......
| | 487 | if (fifo_header.dlc & RX_BUF_FDF)
| | | ~~ ~
| | | | |
| | | | (16) following 'true' branch...
| | | (15) ...to here
| | 488 | skb = alloc_canfd_skb(dev, &cf);
| | | ~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~
| | | | |
| | | | (18) allocated here
| | | (17) ...to here
| |......
| | 491 | if (!skb) {
| | | ~
| | | |
| | | (19) assuming 'skb' is non-NULL
| | | (20) following 'false' branch (when 'skb' is non-NULL)...
| |......
| | 496 | if (fifo_header.dlc & RX_BUF_FDF)
| | | ~~
| | | |
| | | (21) ...to here
| |......
| | 519 | if (err)
| | | ~
| | | |
| | | (22) following 'true' branch...
| | 520 | goto out_fail;
| | | ~~~~
| | | |
| | | (23) ...to here
| |......
| | 537 | return err;
| | | ~~~~~~
| | | |
| | | (24) 'skb' leaks here; was allocated at (18)
| |
---
drivers/net/can/m_can/m_can.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index 2470c47b2e31..f4f54012dea7 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -517,7 +517,7 @@ static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
err = m_can_fifo_read(cdev, fgi, M_CAN_FIFO_DATA,
cf->data, DIV_ROUND_UP(cf->len, 4));
if (err)
- goto out_fail;
+ goto out_free_skb;
}
/* acknowledge rx fifo 0 */
@@ -532,6 +532,8 @@ static int m_can_read_fifo(struct net_device *dev, u32 rxfs)
return 0;
+out_free_skb:
+ kfree_skb(skb);
out_fail:
netdev_err(dev, "FIFO read returned %d\n", err);
return err;
--
2.32.0