[PATCH] PCI: Fix minimum allocation address overwrite

[PATCH] PCI: Fix minimum allocation address overwrite

[Christoph Biedl]

Commit 36e097a8a297 ("PCI: Split out bridge window override of minimum
allocation address") claimed to do no functional changes but unfortunately
did: The "min" variable is altered. At least the AVM A1 PCMCIA adapter was
no longer detected, breaking ISDN operation.

So use a local copy of min to restore the previous behaviour.

Cc: stable@vger.kernel.org      # v3.14+
Fixes: 36e097a8a297 ("PCI: Split out bridge window override of minimum allocation address")
Signed-off-by: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
---
Since I have access to that piece of hardware for a limited time only,
please get back to ASAP in case I should do more tests, by 2015-12-26
the latest.

Additional tests were done for -stable on the latest 3.14, 4.1 and 4.3
releases, with all results as expected.
---
 drivers/pci/bus.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index d3346d2..60263f7 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -140,6 +140,8 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 	type_mask |= IORESOURCE_TYPE_BITS;
 
 	pci_bus_for_each_resource(bus, r, i) {
+		resource_size_t min_used;
+
 		if (!r)
 			continue;
 
@@ -162,13 +164,11 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
 		 * this is an already-configured bridge window, its start
 		 * overrides "min".
 		 */
-		if (avail.start)
-			min = avail.start;
-
+		min_used = avail.start ? : min;
 		max = avail.end;
 
 		/* Ok, try it out.. */
-		ret = allocate_resource(r, res, size, min, max,
+		ret = allocate_resource(r, res, size, min_used, max,
 					align, alignf, alignf_data);
 		if (ret == 0)
 			return 0;
-- 
1.7.10.4

Re: [PATCH] PCI: Fix minimum allocation address overwrite

[Bjorn Helgaas]

On Wed, Dec 23, 2015 at 04:51:57PM +0100, Christoph Biedl wrote:
> Commit 36e097a8a297 ("PCI: Split out bridge window override of minimum
> allocation address") claimed to do no functional changes but unfortunately
> did: The "min" variable is altered. At least the AVM A1 PCMCIA adapter was
> no longer detected, breaking ISDN operation.
> 
> So use a local copy of min to restore the previous behaviour.
> 
> Cc: stable@vger.kernel.org      # v3.14+
> Fixes: 36e097a8a297 ("PCI: Split out bridge window override of minimum allocation address")
> Signed-off-by: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>

Applied to pci/misc for v4.5, thanks!

I don't think the problem is specific to the AVM A1 adapter; it is probably
related to the specific system memory layout and maybe PCMCIA.  If you have
more information, e.g., a dmesg log and /proc/iomem contents, that would be
useful documentation.

> ---
> Since I have access to that piece of hardware for a limited time only,
> please get back to ASAP in case I should do more tests, by 2015-12-26
> the latest.
> 
> Additional tests were done for -stable on the latest 3.14, 4.1 and 4.3
> releases, with all results as expected.
> ---
>  drivers/pci/bus.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index d3346d2..60263f7 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -140,6 +140,8 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
>  	type_mask |= IORESOURCE_TYPE_BITS;
>  
>  	pci_bus_for_each_resource(bus, r, i) {
> +		resource_size_t min_used;
> +
>  		if (!r)
>  			continue;
>  
> @@ -162,13 +164,11 @@ static int pci_bus_alloc_from_region(struct pci_bus *bus, struct resource *res,
>  		 * this is an already-configured bridge window, its start
>  		 * overrides "min".
>  		 */
> -		if (avail.start)
> -			min = avail.start;
> -
> +		min_used = avail.start ? : min;
>  		max = avail.end;
>  
>  		/* Ok, try it out.. */
> -		ret = allocate_resource(r, res, size, min, max,
> +		ret = allocate_resource(r, res, size, min_used, max,
>  					align, alignf, alignf_data);
>  		if (ret == 0)
>  			return 0;
> -- 
> 1.7.10.4
> 
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