linux-kernel - Re: [PATCH 3.12-rc7] KVM: Fix modprobe failure for kvm_intel/kvm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Wed, 30 Oct 2013 17:40:46 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tim Gardner <tim.gardner@...onical.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Gleb Natapov <gleb@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	KVM list <kvm@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 3.12-rc7] KVM: Fix modprobe failure for kvm_intel/kvm_amd

Il 30/10/2013 17:23, Greg KH ha scritto:
>> > static inline struct dentry *debugfs_create_dir(const char *name,
>> >                                                 struct dentry *parent)
>> > {
>> >         return ERR_PTR(-ENODEV);
>> > }
>> > 
>> > which would oops a lot of the current callers.
> It will oops?  Really?  Where?  That shouldn't happen at all.

Doh, it obviously won't because the bogus pointer value will never be
dereferenced by the dummy debugfs_create_file.

>> > Very few places use the currently correct idiom
>> > 
>> > 	if (IS_ERR(root) || !root)
>> > 
>> > but it's very ugly...  Perhaps debugfs_create_dir *should* return an
>> > error-valued pointer after all.
> Or just don't care about the return value, and all will work out just
> fine, right?

Debugfs files would then be created in the debugfs root, which is not nice.

        /* If the parent is not specified, we create it in the root.
         * We need the root dentry to do this, which is in the super 
         * block. A pointer to that is in the struct vfsmount that we
         * have around.
         */
        if (!parent)
                parent = debugfs_mount->mnt_root;

This is all documented right:

/**
 * debugfs_create_file - create a file in the debugfs filesystem
 * ...
 * This function will return a pointer to a dentry if it succeeds.  This
 * pointer must be passed to the debugfs_remove() function when the file is
 * to be removed (no automatic cleanup happens if your module is unloaded,
 * you are responsible here.)  If an error occurs, %NULL will be returned.
 *
 * If debugfs is not enabled in the kernel, the value -%ENODEV will be
 * returned.
 */

so I guess it's just part of the API.

Paolo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/