From: Christoph Hellwig <hch@infradead.org> To: Vivek Goyal <vgoyal@redhat.com> Cc: Christoph Hellwig <hch@infradead.org>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, virtio-fs@redhat.com, miklos@szeredi.hu, stefanha@redhat.com, dgilbert@redhat.com, viro@zeniv.linux.org.uk, dhowells@redhat.com, richard.weinberger@gmail.com, asmadeus@codewreck.org, v9fs-developer@lists.sourceforge.net Subject: Re: [PATCH v2 0/2] Add support to boot virtiofs and 9pfs as rootfs Date: Thu, 17 Jun 2021 15:25:00 +0100 [thread overview] Message-ID: <YMtbPDW+T5Z1uBZt@infradead.org> (raw) In-Reply-To: <20210617133052.GA1142820@redhat.com> On Thu, Jun 17, 2021 at 09:30:52AM -0400, Vivek Goyal wrote: > > +static int __init mount_nodev_root(void) > > +{ > > + struct file_system_type *fs = get_fs_type(root_fs_names); > > get_fs_type() assumes root_fs_names is not null. So if I pass > "root=myfs rw", it crashes with null pointer dereference. Ok, I'll need to fix that. > > + int err = -ENODEV; > > + > > + if (!fs) > > + goto out; > > + if (fs->fs_flags & FS_REQUIRES_DEV) > > + goto out_put_filesystem; > > + > > + fs_names = (void *)__get_free_page(GFP_KERNEL); > > + if (!fs_names) > > + goto out_put_filesystem; > > + get_fs_names(fs_names); > > I am wondering what use case we are trying to address by calling > get_fs_names() and trying do_mount_root() on all filesystems > returned by get_fs_names(). I am assuming following use cases > you have in mind. > > A. User passes a single filesystem in rootfstype. > > root=myfs rootfstype=virtiofs rw > > B. User passes multiple filesystems in rootfstype and kernel tries all > of them one after the other > > root=myfs, rootfstype=9p,virtiofs rw > > C. User does not pass a filesystem type at all. And kernel will get a > list of in-built filesystems and will try these one after the other. > > root=myfs rw > > If that's the thought, will it make sense to call get_fs_names() first > and then inside the for loop call get_fs_type() and try mounting > only if FS_REQUIRES_DEV is not set, otherwise skip and move onto th > next filesystem in the list (fs_names). I thought of A and B. I did not think at all of C and think it is a rather bad idea. I'll revisit the patch to avoid C and will resend it as a formal patch.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org> To: Vivek Goyal <vgoyal@redhat.com> Cc: virtio-fs@redhat.com, dhowells@redhat.com, miklos@szeredi.hu, richard.weinberger@gmail.com, asmadeus@codewreck.org, linux-kernel@vger.kernel.org, Christoph Hellwig <hch@infradead.org>, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, v9fs-developer@lists.sourceforge.net Subject: Re: [Virtio-fs] [PATCH v2 0/2] Add support to boot virtiofs and 9pfs as rootfs Date: Thu, 17 Jun 2021 15:25:00 +0100 [thread overview] Message-ID: <YMtbPDW+T5Z1uBZt@infradead.org> (raw) In-Reply-To: <20210617133052.GA1142820@redhat.com> On Thu, Jun 17, 2021 at 09:30:52AM -0400, Vivek Goyal wrote: > > +static int __init mount_nodev_root(void) > > +{ > > + struct file_system_type *fs = get_fs_type(root_fs_names); > > get_fs_type() assumes root_fs_names is not null. So if I pass > "root=myfs rw", it crashes with null pointer dereference. Ok, I'll need to fix that. > > + int err = -ENODEV; > > + > > + if (!fs) > > + goto out; > > + if (fs->fs_flags & FS_REQUIRES_DEV) > > + goto out_put_filesystem; > > + > > + fs_names = (void *)__get_free_page(GFP_KERNEL); > > + if (!fs_names) > > + goto out_put_filesystem; > > + get_fs_names(fs_names); > > I am wondering what use case we are trying to address by calling > get_fs_names() and trying do_mount_root() on all filesystems > returned by get_fs_names(). I am assuming following use cases > you have in mind. > > A. User passes a single filesystem in rootfstype. > > root=myfs rootfstype=virtiofs rw > > B. User passes multiple filesystems in rootfstype and kernel tries all > of them one after the other > > root=myfs, rootfstype=9p,virtiofs rw > > C. User does not pass a filesystem type at all. And kernel will get a > list of in-built filesystems and will try these one after the other. > > root=myfs rw > > If that's the thought, will it make sense to call get_fs_names() first > and then inside the for loop call get_fs_type() and try mounting > only if FS_REQUIRES_DEV is not set, otherwise skip and move onto th > next filesystem in the list (fs_names). I thought of A and B. I did not think at all of C and think it is a rather bad idea. I'll revisit the patch to avoid C and will resend it as a formal patch.
next prev parent reply other threads:[~2021-06-17 14:25 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-14 17:44 [PATCH v2 0/2] Add support to boot virtiofs and 9pfs as rootfs Vivek Goyal 2021-06-14 17:44 ` [Virtio-fs] " Vivek Goyal 2021-06-14 17:44 ` [PATCH v2 1/2] init/do_mounts.c: Add a path to boot from tag based filesystems Vivek Goyal 2021-06-14 17:44 ` [Virtio-fs] " Vivek Goyal 2021-06-18 7:07 ` Miklos Szeredi 2021-06-18 7:07 ` [Virtio-fs] " Miklos Szeredi 2021-06-18 12:53 ` Vivek Goyal 2021-06-18 12:53 ` [Virtio-fs] " Vivek Goyal 2021-06-14 17:44 ` [PATCH v2 2/2] init/do_mounts.c: Add 9pfs to the list of " Vivek Goyal 2021-06-14 17:44 ` [Virtio-fs] " Vivek Goyal 2021-06-17 10:14 ` [PATCH v2 0/2] Add support to boot virtiofs and 9pfs as rootfs Christoph Hellwig 2021-06-17 10:14 ` [Virtio-fs] " Christoph Hellwig 2021-06-17 13:30 ` Vivek Goyal 2021-06-17 13:30 ` [Virtio-fs] " Vivek Goyal 2021-06-17 14:25 ` Christoph Hellwig [this message] 2021-06-17 14:25 ` Christoph Hellwig
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