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...
Fixes: 79c0b2df79eb (add filesystem subtype support) Cc: David Howells dhowells@redhat.com Signed-off-by: ChenXiaoSong chenxiaosong2@huawei.com --- fs/namespace.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c index 2f3c6a0350a8..396ff1bcfdad 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2490,9 +2490,12 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags, return -ENODEV;
mnt = vfs_kern_mount(type, sb_flags, name, data); - if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && - !mnt->mnt_sb->s_subtype) - mnt = fs_set_subtype(mnt, fstype); + if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE)) { + down_write(&mnt->mnt_sb->s_umount); + if (!mnt->mnt_sb->s_subtype) + mnt = fs_set_subtype(mnt, fstype); + up_write(&mnt->mnt_sb->s_umount); + }
put_filesystem(type); if (IS_ERR(mnt))