On Wed, Aug 10, 2022 at 08:11:33AM +0200, Greg KH wrote: > On Wed, Aug 10, 2022 at 08:54:36AM +0300, Krzysztof Kozlowski wrote: > > On 09/08/2022 22:21, Bjorn Helgaas wrote: > > > [+cc regressions list] > > > > > > 23d99baf9d72 appeared in v5.19-rc1. > > > > > > On Tue, Aug 09, 2022 at 11:29:43AM -0700, Stephen Hemminger wrote: > > >> This commit broke the driver override script in DPDK. > > >> This is an API/ABI breakage, please revert or fix the commit. > > >> > > >> Report of problem: > > >> http://mails.dpdk.org/archives/dev/2022-August/247794.html > > > > Thanks for the report. I'll take a look. > > > > >> > > >> > > >> commit 23d99baf9d729ca30b2fb6798a7b403a37bfb800 > > >> Author: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > > >> Date: Tue Apr 19 13:34:28 2022 +0200 > > >> > > >> PCI: Use driver_set_override() instead of open-coding > > >> > > >> Use a helper to set driver_override to the reduce amount of duplicated > > >> code. Make the driver_override field const char, because it is not > > >> modified by the core and it matches other subsystems. > > >> > > >> Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > > >> Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > > >> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > > >> Link: https://lore.kernel.org/r/20220419113435.246203-6-krzysztof.kozlowski@xxxxxxxxxx > > >> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > >> > > >> > > >> The script is sending single nul character to remove override > > >> and that no longer works. > > > > The sysfs API clearly states: > > "and > > may be cleared with an empty string (echo > driver_override)." > > Documentation/ABI/testing/sysfs-bus-pci > > > > Sending other data and expecting the same result is not conforming to > > API. Therefore we have usual example of some undocumented behavior which > > user-space started relying on and instead using API, user-space expect > > that undocumented behavior to be back. > > > > Yay! I wonder what is the point to even describe the ABI if user-space > > can simply ignore it? > > One can argue that a string of just '\0' is an "empty string" and we > should be able to properly handle this in the kernel. Heck, > "\0\0\0\0\0\0" is also an "empty string", right? > > I don't have an issue with fixing the kernel up here, it should be able > to handle this. Stephen, does the patch below fix this for you? thanks, greg k-h ----------------- diff --git a/drivers/base/driver.c b/drivers/base/driver.c index 15a75afe6b84..676b6275d5b5 100644 --- a/drivers/base/driver.c +++ b/drivers/base/driver.c @@ -63,6 +63,12 @@ int driver_set_override(struct device *dev, const char **override, if (len >= (PAGE_SIZE - 1)) return -EINVAL; + /* + * Compute the real length of the string in case userspace sends us a + * bunch of \0 characters like python likes to do. + */ + len = strlen(s); + if (!len) { /* Empty string passed - clear override */ device_lock(dev);
