[PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

[PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

[Ravi Kumar Bandi]

pci_mmap_resource() does not check IORESOURCE_DISABLED before mapping
a PCI BAR resource into userspace. This allows new mmaps to succeed
even after a device has been marked disabled or soft-unplugged by the
driver to prevent further access.

Add the check to return -ENODEV when the resource is disabled, blocking
new userspace mmaps of BAR resources after device removal.

Tested by marking the PCI BAR resource as disabled and verifying that
a subsequent mmap attempt fails with -ENODEV.

$ sudo python3 -c "
import os, mmap, errno
try:
    fd = os.open('/sys/bus/pci/devices/0001:01:00.0/resource0',os.O_RDONLY)
    mmap.mmap(fd, 4096, access=mmap.ACCESS_READ)
    print('mmap succeeded')
except OSError as e:
    print(f'mmap failed - {e}')
"
mmap failed - [Errno 19] No such device
$

Signed-off-by: Ravi Kumar Bandi <ravib@amazon.com>
---
 drivers/pci/pci-sysfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index d37860841260..61ae259f8ca8 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1089,6 +1089,9 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
 	if (ret)
 		return ret;
 
+	if (res->flags & IORESOURCE_DISABLED)
+		return -ENODEV;
+
 	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
 		return -EINVAL;
 
-- 
2.47.3

Re: [PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

[Krzysztof Wilczyński]

Hello,

> pci_mmap_resource() does not check IORESOURCE_DISABLED before mapping
> a PCI BAR resource into userspace. This allows new mmaps to succeed
> even after a device has been marked disabled or soft-unplugged by the
> driver to prevent further access.

Which driver disables resources?  Would this be some Amazon-specific thing
you are trying to fix?  Or are you just manually disabling a given device
using sysfs, or something like this?

For "soft-unplugged" device we have pci_dev_set_disconnected(), but this
does not check current flags set.

What is your use case here?

> Add the check to return -ENODEV when the resource is disabled, blocking
> new userspace mmaps of BAR resources after device removal.
> 
> Tested by marking the PCI BAR resource as disabled and verifying that
> a subsequent mmap attempt fails with -ENODEV.

Can you explain how did you do this?

> @@ -1089,6 +1089,9 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
>  	if (ret)
>  		return ret;
>  
> +	if (res->flags & IORESOURCE_DISABLED)
> +		return -ENODEV;
> +

This probably would be better if it checked IORESOURCE_DISABLED and
IORESOURCE_UNSET, but then probably using resource_assigned() would
be even better.

Thank you!

	Krzysztof

Re: [PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

[Ilpo Järvinen]

[-- Attachment #1: Type: text/plain, Size: 1706 bytes --]

On Tue, 12 May 2026, Krzysztof Wilczyński wrote:

> Hello,
> 
> > pci_mmap_resource() does not check IORESOURCE_DISABLED before mapping
> > a PCI BAR resource into userspace. This allows new mmaps to succeed
> > even after a device has been marked disabled or soft-unplugged by the
> > driver to prevent further access.
> 
> Which driver disables resources?  Would this be some Amazon-specific thing
> you are trying to fix?  Or are you just manually disabling a given device
> using sysfs, or something like this?
> 
> For "soft-unplugged" device we have pci_dev_set_disconnected(), but this
> does not check current flags set.
> 
> What is your use case here?
> 
> > Add the check to return -ENODEV when the resource is disabled, blocking
> > new userspace mmaps of BAR resources after device removal.
> > 
> > Tested by marking the PCI BAR resource as disabled and verifying that
> > a subsequent mmap attempt fails with -ENODEV.
> 
> Can you explain how did you do this?
> 
> > @@ -1089,6 +1089,9 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
> >  	if (ret)
> >  		return ret;
> >  
> > +	if (res->flags & IORESOURCE_DISABLED)
> > +		return -ENODEV;
> > +
> 
> This probably would be better if it checked IORESOURCE_DISABLED and
> IORESOURCE_UNSET, but then probably using resource_assigned() would
> be even better.

Yes, resource_assigned() makes more sense.

When considering Krzysztof's sysfs rework series in pci/sysfs, this all 
should be handled in .is_visible and not in pci_mmap_resource().

Also (FYI), alpha has its own pci_mmap_resource() (IIRC, it still has it 
even after Krzysztof's series).

-- 
 i.

Re: [PATCH] PCI/sysfs: Check IORESOURCE_DISABLED in resource mmap handler

[Krzysztof Wilczyński]

Hello,

> > > pci_mmap_resource() does not check IORESOURCE_DISABLED before mapping
> > > a PCI BAR resource into userspace. This allows new mmaps to succeed
> > > even after a device has been marked disabled or soft-unplugged by the
> > > driver to prevent further access.
> > 
> > Which driver disables resources?  Would this be some Amazon-specific thing
> > you are trying to fix?  Or are you just manually disabling a given device
> > using sysfs, or something like this?
> > 
> > For "soft-unplugged" device we have pci_dev_set_disconnected(), but this
> > does not check current flags set.
> > 
> > What is your use case here?
> > 
> > > Add the check to return -ENODEV when the resource is disabled, blocking
> > > new userspace mmaps of BAR resources after device removal.
> > > 
> > > Tested by marking the PCI BAR resource as disabled and verifying that
> > > a subsequent mmap attempt fails with -ENODEV.
> > 
> > Can you explain how did you do this?
> > 
> > > @@ -1089,6 +1089,9 @@ static int pci_mmap_resource(struct kobject *kobj, const struct bin_attribute *a
> > >  	if (ret)
> > >  		return ret;
> > >  
> > > +	if (res->flags & IORESOURCE_DISABLED)
> > > +		return -ENODEV;
> > > +
> > 
> > This probably would be better if it checked IORESOURCE_DISABLED and
> > IORESOURCE_UNSET, but then probably using resource_assigned() would
> > be even better.
> 
> Yes, resource_assigned() makes more sense.
> 
> When considering Krzysztof's sysfs rework series in pci/sysfs, this all 
> should be handled in .is_visible and not in pci_mmap_resource().

We can't use the resource_assigned() sadly, but the flags is something we
definitely can check - I will add this, test, and send new series.

The callback, though, will be called on creation, or if someone calls
remove, create or update for the sysfs resource group - no driver does this
at the moment (some DRM drivers resize resources, but that's unrelated),
so I am not sure how Ravi is doing this at runtime.  Perhaps I am looking
wrong at the code somewhere...

> Also (FYI), alpha has its own pci_mmap_resource() (IIRC, it still has it 
> even after Krzysztof's series).

For the sparse/dense resources, yes.

Thank you!

	Krzysztof