[PATCH] PCI: Don't read config space of disconnected devices in ext cap search

[PATCH] PCI: Don't read config space of disconnected devices in ext cap search

[Anthony Pighin]

Commit 4d909bf1a53e ("PCI: Refactor extended capability search into
PCI_FIND_NEXT_EXT_CAP()") moved the extended capability search from the
device config accessor to the bus config accessor. The bus accessor
skips the disconnected device check, so walking the extended capability
list of a device already marked disconnected (surprise removal, AER/DPC
recovery) now issues real config reads to it. A dead device returns all
ones for the first extended capability header. That decodes as a next
pointer to the last dword of config space, so the walk keeps re-reading
that dword until its TTL expires, roughly 480 config reads per call.

Restore the device accessor so the walk stops without touching hardware
once the device is disconnected.

Fixes: 4d909bf1a53e ("PCI: Refactor extended capability search into PCI_FIND_NEXT_EXT_CAP()")
Cc: stable@vger.kernel.org
Signed-off-by: Anthony Pighin <anthony.pighin@nokia.com>
---
 drivers/pci/pci.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d79d2ee4ac69..908d2273466b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -519,8 +519,7 @@ u16 pci_find_next_ext_capability(struct pci_dev *dev, u16 start, int cap)
 	if (dev->cfg_size <= PCI_CFG_SPACE_SIZE)
 		return 0;
 
-	return PCI_FIND_NEXT_EXT_CAP(pci_bus_read_config, start, cap,
-				     NULL, dev->bus, dev->devfn);
+	return PCI_FIND_NEXT_EXT_CAP(pci_read_config, start, cap, NULL, dev);
 }
 EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
 
-- 
2.43.0

Re: [PATCH] PCI: Don't read config space of disconnected devices in ext cap search

[sashiko-bot]

> Commit 4d909bf1a53e ("PCI: Refactor extended capability search into
> PCI_FIND_NEXT_EXT_CAP()") moved the extended capability search from the
> device config accessor to the bus config accessor. The bus accessor
> skips the disconnected device check, so walking the extended capability
> list of a device already marked disconnected (surprise removal, AER/DPC
> recovery) now issues real config reads to it. A dead device returns all
> ones for the first extended capability header. That decodes as a next
> pointer to the last dword of config space, so the walk keeps re-reading
> that dword until its TTL expires, roughly 480 config reads per call.
> 
> Restore the device accessor so the walk stops without touching hardware
> once the device is disconnected.
> 
> Fixes: 4d909bf1a53e ("PCI: Refactor extended capability search into PCI_FIND_NEXT_EXT_CAP()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Anthony Pighin <anthony.pighin@nokia.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261019165159.1268120-1-anthony.pighin@nokia.com?part=1