[resent, hopefully with slightly less formatting damage]
On 17/10/2018 16:45, David Howells wrote:
Alan Jenkins <alan.christopher.jenkins@xxxxxxxxx> 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;
+
fc = vfs_new_fs_context(target.dentry->d_sb->s_type, target.dentry,
0, 0, FS_CONTEXT_FOR_RECONFIGURE);
if (IS_ERR(fc)) {
( the "if" statement it adds to fspick() is equivalent to the second
"if" statement in do_remount(): )
static int do_remount(struct path *path, int ms_flags, int sb_flags,
int mnt_flags, void *data)
{
int err;
struct super_block *sb = path->mnt->mnt_sb;
struct mount *mnt = real_mount(path->mnt);
if (!check_mnt(mnt))
return -EINVAL;
if (path->dentry != path->mnt->mnt_root)
return -EINVAL;
Thanks
Alan
