Re: UAF in moxart_remove

[Greg KH <greg@kroah.com>]

On Tue, Jan 11, 2022 at 01:10:51PM +0100, Greg KH wrote:
> On Tue, Jan 11, 2022 at 09:35:11AM +0100, Marcus Meissner wrote:
> > Hi whitehat002,
> > 
> > SUSE currently does not build the moxart driver, let me defer you to
> > security@kernel.org and the MMC maintainers.
> > 
> > i also opened a bug in our bugzilla just for tracking
> > https://bugzilla.suse.com/show_bug.cgi?id=1194516
> > 
> > Ciao, Marcus
> > On Tue, Jan 11, 2022 at 02:30:32PM +0800, whitehat002 whitehat002 wrote:
> > > Hello suse security team,
> > > 
> > > There is a UAF in drivers/mmc/host/moxart-mmc.c
> > > This is similar with
> > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=42933c8aa14be1caa9eda41f65cde8a3a95d3e39
> > > 
> > > 
> > > 
> > > static int moxart_remove(struct platform_device *pdev)
> > > {
> > > struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
> > > struct moxart_host *host = mmc_priv(mmc);
> > > 
> > > dev_set_drvdata(&pdev->dev, NULL);
> > > 
> > > if (!IS_ERR_OR_NULL(host->dma_chan_tx))
> > > dma_release_channel(host->dma_chan_tx);
> > > if (!IS_ERR_OR_NULL(host->dma_chan_rx))
> > > dma_release_channel(host->dma_chan_rx);
> > > mmc_remove_host(mmc);
> > > mmc_free_host(mmc);   //[0] free
> > > 
> > > writel(0, host->base + REG_INTERRUPT_MASK); //[1] host is private data from
> > > mmc_host UAF
> > > writel(0, host->base + REG_POWER_CONTROL);
> > > writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
> > >        host->base + REG_CLOCK_CONTROL);
> > > 
> > > return 0;
> > > }
> > > 
> 
> Can you write a patch to fix this so that you can get proper credit for
> fixing it as well as finding it?

Here's a untested patch that "should" be correct, can someone test it
please?

thanks,

greg k-h


diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
index 16d1c7a43d33..fe05ae81afd9 100644
--- a/drivers/mmc/host/moxart-mmc.c
+++ b/drivers/mmc/host/moxart-mmc.c
@@ -704,14 +704,14 @@ static int moxart_remove(struct platform_device *pdev)
 		dma_release_channel(host->dma_chan_tx);
 	if (!IS_ERR_OR_NULL(host->dma_chan_rx))
 		dma_release_channel(host->dma_chan_rx);
-	mmc_remove_host(mmc);
-	mmc_free_host(mmc);
-
 	writel(0, host->base + REG_INTERRUPT_MASK);
 	writel(0, host->base + REG_POWER_CONTROL);
 	writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
 	       host->base + REG_CLOCK_CONTROL);
 
+	mmc_remove_host(mmc);
+	mmc_free_host(mmc);
+
 	return 0;
 }