Messages in this thread | | | Subject | Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12] | From | Alan Jenkins <> | Date | Wed, 17 Oct 2018 18:41:24 +0100 |
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On 17/10/2018 16:45, David Howells wrote: > Alan Jenkins <alan.christopher.jenkins@gmail.com> wrote: > >> I agree. I'm happy to see this is using the same check as do_remount(). >> >> >> * change filesystem flags. dir should be a physical root of filesystem. >> * If you've mounted a non-root directory somewhere and want to do remount >> * on it - tough luck. >> */ > Are you suggesting that it should only work at the ultimate root of a > superblock and not a bind mount somewhere within? > > That's tricky to make work for NFS because s_root is a dummy dentry. > > David
Retro-actively: I do not suggest that.
I tried to answer this question in my reply to Eric correcting me. Eric was right to correct me. I now understand the comment above do_remount() is incorrect. I re-reviewed your diff in light of that. I re-endorse your diff as a way to solve the problem I raised.
(I think it would be useful to remove the misleading comment above do_remount(), to avoid future confusion.)
> @@ -186,6 +186,10 @@ SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags
> if (ret < 0) > goto err; > > + ret = -EINVAL; > + if (target.mnt->mnt_root != target.dentry) > + goto err_path; > +
( the "if" statement it adds to fspick() is equivalent to the second "if" statement in do_remount(): )
static int do_remount <https://elixir.bootlin.com/linux/v4.18/ident/do_remount>(struct path <https://elixir.bootlin.com/linux/v4.18/ident/path> *path <https://elixir.bootlin.com/linux/v4.18/ident/path>, int ms_flags, int sb_flags, int mnt_flags, void *data) { int err; struct super_block <https://elixir.bootlin.com/linux/v4.18/ident/super_block> *sb = path <https://elixir.bootlin.com/linux/v4.18/ident/path>->mnt <https://elixir.bootlin.com/linux/v4.18/ident/mnt>->mnt_sb; struct mount <https://elixir.bootlin.com/linux/v4.18/ident/mount> *mnt <https://elixir.bootlin.com/linux/v4.18/ident/mnt> = real_mount <https://elixir.bootlin.com/linux/v4.18/ident/real_mount>(path <https://elixir.bootlin.com/linux/v4.18/ident/path>->mnt <https://elixir.bootlin.com/linux/v4.18/ident/mnt>);
if (!check_mnt <https://elixir.bootlin.com/linux/v4.18/ident/check_mnt>(mnt <https://elixir.bootlin.com/linux/v4.18/ident/mnt>)) return -EINVAL <https://elixir.bootlin.com/linux/v4.18/ident/EINVAL>;
if (path <https://elixir.bootlin.com/linux/v4.18/ident/path>->dentry != path <https://elixir.bootlin.com/linux/v4.18/ident/path>->mnt <https://elixir.bootlin.com/linux/v4.18/ident/mnt>->mnt_root) return -EINVAL <https://elixir.bootlin.com/linux/v4.18/ident/EINVAL>;
Thanks
Alan
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