Allow atomic exchange via RENAME_EXCHANGE when using simple_rename.
This affects binderfs, ramfs, hubetlbfs and bpffs.
Signed-off-by: Lorenz Bauer <[email protected]>
---
fs/libfs.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index 1cf144dc9ed2..ba7438ab9371 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -479,9 +479,12 @@ int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
struct inode *inode = d_inode(old_dentry);
int they_are_dirs = d_is_dir(old_dentry);
- if (flags & ~RENAME_NOREPLACE)
+ if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
return -EINVAL;
+ if (flags & RENAME_EXCHANGE)
+ return simple_rename_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
if (!simple_empty(new_dentry))
return -ENOTEMPTY;
--
2.32.0
On Thu, 28 Oct 2021 at 11:48, Lorenz Bauer <[email protected]> wrote:
>
> Allow atomic exchange via RENAME_EXCHANGE when using simple_rename.
> This affects binderfs, ramfs, hubetlbfs and bpffs.
Ramfs and hugetlbfs are generic enough; those seem safe.
Binderfs: I have no idea what this does; binderfs_rename() should
probably error out on RENAME_EXCHANGE for now, or an explicit ack from
the maintainers.
Bpffs is your baby...
Thanks,
Miklos
On 11/2/21 10:25 AM, Miklos Szeredi wrote:
> On Thu, 28 Oct 2021 at 11:48, Lorenz Bauer <[email protected]> wrote:
>>
>> Allow atomic exchange via RENAME_EXCHANGE when using simple_rename.
>> This affects binderfs, ramfs, hubetlbfs and bpffs.
>
> Ramfs and hugetlbfs are generic enough; those seem safe.
>
> Binderfs: I have no idea what this does; binderfs_rename() should
> probably error out on RENAME_EXCHANGE for now, or an explicit ack from
> the maintainers.
Thanks for the review, Miklos! Adding Christian to Cc wrt binderfs ... full context
for all patches: https://lore.kernel.org/bpf/[email protected]/
> Bpffs is your baby...
>
> Thanks,
> Miklos
>
On Tue, Nov 02, 2021 at 11:11:02AM +0100, Daniel Borkmann wrote:
> On 11/2/21 10:25 AM, Miklos Szeredi wrote:
> > On Thu, 28 Oct 2021 at 11:48, Lorenz Bauer <[email protected]> wrote:
> > >
> > > Allow atomic exchange via RENAME_EXCHANGE when using simple_rename.
> > > This affects binderfs, ramfs, hubetlbfs and bpffs.
> >
> > Ramfs and hugetlbfs are generic enough; those seem safe.
> >
> > Binderfs: I have no idea what this does; binderfs_rename() should
Fwiw, allows dynamic creation and removal of Android binder ipc
devices. Each mount is a separate instance and it's mountable inside
unprivileged containers. Since Android 12 default how binder devices are
managed. Also makes it possibe to run Android in unprivileged
containers.
> > probably error out on RENAME_EXCHANGE for now, or an explicit ack from
> > the maintainers.
>
> Thanks for the review, Miklos! Adding Christian to Cc wrt binderfs ... full context
> for all patches: https://lore.kernel.org/bpf/[email protected]/
Yep, I saw that. Seems good.
> probably error out on RENAME_EXCHANGE for now, or an explicit ack from
> the maintainers.
I don't think there is any issue in allowing binderfs to support this.
Binderfs files are always device nodes. Allowing them to be atomically
renamed shouldn't be a problem. So:
Acked-by: Christian Brauner <[email protected]>
Christian