From 647e82dbf85124697be59a4b4cf00c0d38177dcb Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Thu, 1 Sep 2022 14:34:06 +0300 Subject: [PATCH] platform/x86: p2sb: Fix UAF when caller uses resource name 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 Suggested-by: Mika Westerberg 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 Link: https://lore.kernel.org/r/20220901113406.65876-1-andriy.shevchenko@linux.intel.com Reviewed-by: Hans de Goede Signed-off-by: Hans de Goede --- drivers/platform/x86/p2sb.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/platform/x86/p2sb.c b/drivers/platform/x86/p2sb.c index fb2e141f3eb84..384d0962ae93a 100644 --- a/drivers/platform/x86/p2sb.c +++ b/drivers/platform/x86/p2sb.c @@ -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; } -- 2.39.5