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.
