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platform/x86: p2sb: Fix UAF when caller uses resource name

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We have to copy only selected fields from the original resource.
Because a PCI device will be removed immediately after getting
its resources, we may not use any allocated data, hence we may
not copy any pointers.

Consider the following scenario:

  1/ a caller of p2sb_bar() gets the resource;

  2/ the resource has been copied by platform_device_add_data()
     in order to create a platform device;

  3/ the platform device creation will call for the device driver's
     ->probe() as soon as a match found;

  4/ the ->probe() takes given resources (see 2/) and tries to
     access one of its field, i.e. 'name', in the
     __devm_ioremap_resource() to create a pretty looking output;

  5/ but the 'name' is a dangling pointer because p2sb_bar()
     removed a PCI device, which 'name' had been copied to
     the caller's memory.

  6/ UAF (Use-After-Free) as a result.

Kudos to Mika for the initial analisys of the issue.

Fixes: 9745fb07474f ("platform/x86/intel: Add Primary to Sideband (P2SB) bridge support")
Reported-by: kernel test robot <oliver.sang@intel.com>
Suggested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/linux-i2c/YvPCbnKqDiL2XEKp@xsang-OptiPlex-9020/
Link: https://lore.kernel.org/linux-i2c/YtjAswDKfiuDfWYs@xsang-OptiPlex-9020/
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220901113406.65876-1-andriy.shevchenko@linux.intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
This commit is contained in:
Andy Shevchenko 2022-09-01 14:34:06 +03:00 committed by Hans de Goede
parent 5542dfc582
commit 647e82dbf8
1 changed files with 16 additions and 2 deletions
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18
drivers/platform/x86/p2sb.c
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@ -42,10 +42,24 @@ static int p2sb_get_devfn(unsigned int *devfn)
return 0;
}
/* Copy resource from the first BAR of the device in question */
static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
{
/* Copy resource from the first BAR of the device in question */
*mem = pdev->resource[0];
struct resource *bar0 = &pdev->resource[0];
/* Make sure we have no dangling pointers in the output */
memset(mem, 0, sizeof(*mem));
/*
* We copy only selected fields from the original resource.
* Because a PCI device will be removed soon, we may not use
* any allocated data, hence we may not copy any pointers.
*/
mem->start = bar0->start;
mem->end = bar0->end;
mem->flags = bar0->flags;
mem->desc = bar0->desc;
return 0;
}