On Tue, 2024-01-23 at 12:46 -0600, Bjorn Helgaas wrote:
On Thu, Jan 11, 2024 at 09:55:36AM +0100, Philipp Stanner wrote:
pci_iounmap() in lib/pci_iomap.c is supposed to check whether an address is within ioport-range IF the config specifies that ioports exist. If so, the port should be unmapped with ioport_unmap(). If not, it's a generic MMIO address that has to be passed to iounmap().
The bugs are: 1. ioport_unmap() is missing entirely, so this function will never actually unmap a port.
The preceding comment suggests that in this default implementation, the ioport does not need unmapping, and it wasn't something it was supposed to do but just failed to do:
* NOTE! This default implementation assumes that if the architecture * support ioport mapping (HAS_IOPORT_MAP), the ioport mapping will * be fixed to the range [ PCI_IOBASE, PCI_IOBASE+IO_SPACE_LIMIT [, * and does not need unmapping with 'ioport_unmap()'. * * If you have different rules for your architecture, you need to * implement your own pci_iounmap() that knows the rules for where * and how IO vs MEM get mapped.
Almost all ioport_unmap() implementations are empty, so in most cases it's a no-op (parisc is an exception).
That sounds correct.
I'm happy to add the ioport_unmap() even just for symmetry, but if we do, I think we should update or remove that comment.
Yes, I think it's the right way: either all architectures should provide ioport_unmap(), empty or not, or all should use a centralized PCI function
I can remove the wrong statement.
2. the #ifdef for the ioport-ranges accidentally also guards iounmap(), potentially compiling an empty function. This would cause the mapping to be leaked.
Implement the missing call to ioport_unmap().
Move the guard so that iounmap() will always be part of the function.
I think we should fix this bug in a separate patch because the ioport_unmap() is much more subtle and doesn't need to be complicated with this fix.
If we agree that one is a bug and the other isn't, then ACK, we should probably split it.
CC: stable@vger.kernel.org # v5.15+ Fixes: 316e8d79a095 ("pci_iounmap'2: Electric Boogaloo: try to make sense of it all") Reported-by: Danilo Krummrich dakr@redhat.com
Is there a URL we can include for Danilo's report? I found https://lore.kernel.org/all/a6ef92ae-0747-435b-822d-d0229da4683c@redhat.com/ , but I'm not sure that's the right part of the conversation.
He pointed out it's a bug in an offlist conversation with me. The link you provided is his only public statement about the topic. The Reported-by served more acknowledging the contribution than issue- tracking
P.
Suggested-by: Arnd Bergmann arnd@kernel.org Signed-off-by: Philipp Stanner pstanner@redhat.com Reviewed-by: Arnd Bergmann arnd@arndb.de
lib/pci_iomap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/lib/pci_iomap.c b/lib/pci_iomap.c index ce39ce9f3526..6e144b017c48 100644 --- a/lib/pci_iomap.c +++ b/lib/pci_iomap.c @@ -168,10 +168,12 @@ void pci_iounmap(struct pci_dev *dev, void __iomem *p) uintptr_t start = (uintptr_t) PCI_IOBASE; uintptr_t addr = (uintptr_t) p; - if (addr >= start && addr < start + IO_SPACE_LIMIT) + if (addr >= start && addr < start + IO_SPACE_LIMIT) { + ioport_unmap(p); return; - iounmap(p); + } #endif + iounmap(p); } EXPORT_SYMBOL(pci_iounmap); -- 2.43.0