Re: [PATCH 4.19,v2] VFS: Fix fuseblk memory leak caused by mount concurrency

[chenxiaosong (A)]

在 2021/10/13 18:38, chenxiaosong (A) 写道:
> 在 2021/10/13 18:11, Greg KH 写道:
> > On Wed, Oct 13, 2021 at 05:51:01PM +0800, ChenXiaoSong wrote:
> > > If two processes mount same superblock, memory leak occurs:
> > >
> > > CPU0               |  CPU1
> > > do_new_mount       |  do_new_mount
> > >    fs_set_subtype   |    fs_set_subtype
> > >      kstrdup        |
> > >                     |      kstrdup
> > >      memrory leak   |
> > >
> > > Fix this by adding a write lock while calling fs_set_subtype.
> > >
> > > Linus's tree already have refactoring patchset [1], one of them can 
> > > fix this bug:
> > >          c30da2e981a7 (fuse: convert to use the new mount API)
> > >
> > > Since we did not merge the refactoring patchset in this branch, I 
> > > create this patch.
> > >
> > > [1] 
> > > https://patchwork.kernel.org/project/linux-fsdevel/patch/20190903113640.7984-3-mszeredi@xxxxxxxxxx/ 
> > >
> > >
> > > Fixes: 79c0b2df79eb (add filesystem subtype support)
> > > Cc: David Howells <dhowells@xxxxxxxxxx>
> > > Signed-off-by: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>
> > > ---
> > > v1: Can not mount sshfs ([PATCH linux-4.19.y] VFS: Fix fuseblk memory 
> > > leak caused by mount concurrency)
> > > v2: Use write lock while writing superblock
> > >
> > >   fs/namespace.c | 9 ++++++---
> > >   1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > As you are referring to a fuse-only patch above, why are you trying to
> > resolve this issue in the core namespace code instead?
> >
> > How does fuse have anything to do with this?
> >
> > confused,
> >
> > greg k-h
> > .
>
> Now, only `fuse_fs_type` and `fuseblk_fs_type` has `FS_HAS_SUBTYPE` flag 
> in kernel code, but maybe there is a filesystem module(`struct 
> file_system_type` has `FS_HAS_SUBTYPE` flag). And only mounting fuseblk 
> filesystem(e.g. ntfs) will occur memory leak now.

How about updating the subject as: VFS: Fix memory leak caused by 
mounting fs with subtype concurrency?