[lvc-project] [PATCH] f2fs: ensure that node info flags are always initialized

[Dmitry Antipov]

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 at syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=5141f6db57a2f7614352
Fixes: e05df3b115e7 ("f2fs: add node operations")
Signed-off-by: Dmitry Antipov <dmantipov at 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 };
 	struct page *page;
 	int err;
 
-- 
2.47.1