On 5/28/20 2:23 PM, Greg Kroah-Hartman wrote: > On Thu, May 28, 2020 at 12:04:32PM +0000, Enderborg, Peter wrote: >> On 5/28/20 11:27 AM, Greg Kroah-Hartman wrote: >>> On Thu, May 28, 2020 at 08:39:02AM +0000, Enderborg, Peter wrote: >>>> On 5/28/20 10:27 AM, Greg Kroah-Hartman wrote: >>>>> On Thu, May 28, 2020 at 10:00:31AM +0200, Peter Enderborg wrote: >>>>>> Since debugfs include sensitive information it need to be treated >>>>>> carefully. But it also has many very useful debug functions for >>>>>> userspace. >>>>>> With this option we can have same configuration for system with >>>>>> need of debugfs and a way to turn it off. It is needed new >>>>>> kernel command line parameter to be activated. >>>>> By "configuration" do you mean "kernel configuration"? What is wrong >>>>> with relying on the build option like we do today? >>>>> >>>>> You might want to reword all of this to make more sense about the >>>>> "problem" you are trying to solve here, as I don't really understand it, >>>>> sorry. >>>>> >>>>> >>>>>> Signed-off-by: Peter Enderborg <peter.enderb...@sony.com> >>>>>> --- >>>>>> fs/debugfs/inode.c | 17 ++++++++++++++++- >>>>>> lib/Kconfig.debug | 10 ++++++++++ >>>>>> 2 files changed, 26 insertions(+), 1 deletion(-) >>>>> No documentation update? That's not good :( >>>>> >>>>> >>>>>> diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c >>>>>> index b7f2e971ecbc..bde37dab77e0 100644 >>>>>> --- a/fs/debugfs/inode.c >>>>>> +++ b/fs/debugfs/inode.c >>>>>> @@ -786,10 +786,25 @@ bool debugfs_initialized(void) >>>>>> } >>>>>> EXPORT_SYMBOL_GPL(debugfs_initialized); >>>>>> >>>>>> +static int allow_debugfs; >>>>>> + >>>>>> +static int __init debugfs_kernel(char *str) >>>>>> +{ >>>>>> + if (str && !strcmp(str, "true")) >>>>>> + allow_debugfs = true; >>>>>> + >>>>>> + return 0; >>>>>> + >>>>>> +} >>>>>> +early_param("debugfs", debugfs_kernel); >>>>>> + >>>>>> static int __init debugfs_init(void) >>>>>> { >>>>>> int retval; >>>>>> - >>>>>> +#ifdef CONFIG_DEBUG_FS_MOUNT_RESTRICTED >>>>>> + if (!allow_debugfs) >>>>>> + return -EPERM; >>>>>> +#endif >>>>> But you are not restricting the ability to mount it here, you are >>>>> removing the ability for it to even start up at all. What does this >>>>> break for code that thinks the filesystem is registered (i.e. the call >>>>> to simple_pin_fs() in start_creating() in fs/debugfs/inode.c? >>>>> >>>> If it does, the lines below is also cause the same problem. >>> In a working system, errors in the lines below will never happen :) >> I think it is not unreasonable to expect that debug functionality are robust >> enough to handle >> system where not everything is working smoothly. > I do not disagree, but have you tested this to ensure that your kernel > still works when you disable debugfs in this manner?
So far only tested on fedora f32 (x86_64) and older arm64 systems. So far only zswap that prints out that "debugfs initialization failed" and it still works fine. > If so, great! Just trying to point out a potential problem... Will do new patchset, im waiting a bit longer to see if there some other comments first. > thanks, > > greg k-h