Re: [PATCH] f2fs: ensure that node info flags are always initialized

[Chao Yu <chao@kernel.org>]

On 2024/12/4 14:09, Dmitry Antipov wrote:
> Syzbot has reported the following KMSAN splat:
> 
> BUG: KMSAN: uninit-value in f2fs_new_node_page+0x1494/0x1630
>   f2fs_new_node_page+0x1494/0x1630
>   f2fs_new_inode_page+0xb9/0x100
>   f2fs_init_inode_metadata+0x176/0x1e90
>   f2fs_add_inline_entry+0x723/0xc90
>   f2fs_do_add_link+0x48f/0xa70
>   f2fs_symlink+0x6af/0xfc0
>   vfs_symlink+0x1f1/0x470
>   do_symlinkat+0x471/0xbc0
>   __x64_sys_symlink+0xcf/0x140
>   x64_sys_call+0x2fcc/0x3d90
>   do_syscall_64+0xd9/0x1b0
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Local variable new_ni created at:
>   f2fs_new_node_page+0x9d/0x1630
>   f2fs_new_inode_page+0xb9/0x100
> 
> So adjust 'f2fs_new_node_page()' to ensure that 'flag' field of on-stack
> 'struct node_info' is always zeroed just like if it was allocated within
> 'struct nat_entry' via 'f2fs_kmem_cache_alloc(..., GFP_F2FS_ZERO, ...)'
> in '__alloc_nat_entry()'.
> 
> Reported-by: syzbot+5141f6db57a2f7614352@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=5141f6db57a2f7614352
> Fixes: e05df3b115e7 ("f2fs: add node operations")
> Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
> ---
>   fs/f2fs/node.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 0b900a7a48e5..5103cc0d95c4 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1314,7 +1314,7 @@ struct page *f2fs_new_inode_page(struct inode *inode)
>   struct page *f2fs_new_node_page(struct dnode_of_data *dn, unsigned int ofs)
>   {
>   	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
> -	struct node_info new_ni;
> +	struct node_info new_ni = { .flag = 0 };

We can initialize new_ni.flag in f2fs_get_node_info() to cover
all similar cases?

Thanks,

>   	struct page *page;
>   	int err;
>