On Wed, Oct 13, 2021 at 06:49:06PM +0800, chenxiaosong (A) wrote: > 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? That would be a better idea, but still, this is not obvious that this is the correct fix at all...
