From: Colin Ian King <colin.king@canonical.com>
To: Lukasz Majewski <lukma@denx.de>, Mark Brown <broonie@kernel.org>,
linux-spi@vger.kernel.org
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: re: spi: Add call to spi_slave_abort() function when spidev driver is released
Date: Thu, 26 Sep 2019 11:00:19 +0100 [thread overview]
Message-ID: <f4db4595-7673-f2ae-4222-cbb9c2d771f9@canonical.com> (raw)
Hi,
Static analysis with Coverity has detected an potential dereference of a
free'd object with commit:
commit 9f918a728cf86b2757b6a7025e1f46824bfe3155
Author: Lukasz Majewski <lukma@denx.de>
Date: Wed Sep 25 11:11:42 2019 +0200
spi: Add call to spi_slave_abort() function when spidev driver is
released
In spidev_release() in drivers/spi/spidev.c the analysis is as follows:
600static int spidev_release(struct inode *inode, struct file *filp)
601{
602 struct spidev_data *spidev;
603
604 mutex_lock(&device_list_lock);
1. alias: Assigning: spidev = filp->private_data. Now both point to
the same storage.
605 spidev = filp->private_data;
606 filp->private_data = NULL;
607
608 /* last close? */
609 spidev->users--;
2. Condition !spidev->users, taking true branch.
610 if (!spidev->users) {
611 int dofree;
612
613 kfree(spidev->tx_buffer);
614 spidev->tx_buffer = NULL;
615
616 kfree(spidev->rx_buffer);
617 spidev->rx_buffer = NULL;
618
619 spin_lock_irq(&spidev->spi_lock);
3. Condition spidev->spi, taking false branch.
620 if (spidev->spi)
621 spidev->speed_hz = spidev->spi->max_speed_hz;
622
623 /* ... after we unbound from the underlying device? */
4. Condition spidev->spi == NULL, taking true branch.
624 dofree = (spidev->spi == NULL);
625 spin_unlock_irq(&spidev->spi_lock);
626
5. Condition dofree, taking true branch.
627 if (dofree)
6. freed_arg: kfree frees spidev.
628 kfree(spidev);
629 }
630#ifdef CONFIG_SPI_SLAVE
CID 89726 (#1 of 1): Read from pointer after free (USE_AFTER_FREE)
7. deref_after_free: Dereferencing freed pointer spidev.
631 spi_slave_abort(spidev->spi);
632#endif
633 mutex_unlock(&device_list_lock);
634
635 return 0;
636}
The call to spi_slave_abort() on spidev is reading an earlier kfree'd
spidev.
Colin
next reply other threads:[~2019-09-26 10:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-26 10:00 Colin Ian King [this message]
2019-09-26 10:14 ` Lukasz Majewski
2019-09-26 10:15 ` Colin Ian King
2019-09-26 10:32 ` Geert Uytterhoeven
2019-09-26 12:49 ` Lukasz Majewski
2019-09-26 13:51 ` Geert Uytterhoeven
2019-09-26 14:06 ` Lukasz Majewski
2019-09-26 15:17 ` Mark Brown
2019-09-26 22:38 ` Lukasz Majewski
2019-10-07 17:02 ` Mark Brown
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