linux-kernel - Re: [f2fs-dev] KMSAN: uninit-value in f2fs

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Message-ID: <20200925163819.GA3315208@gmail.com>
Date:   Fri, 25 Sep 2020 09:38:19 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     syzbot <syzbot+0eac6f0bbd558fd866d7@...kaller.appspotmail.com>,
        chao@...nel.org, glider@...gle.com, jaegeuk@...nel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [f2fs-dev] KMSAN: uninit-value in f2fs_lookup

On Fri, Sep 25, 2020 at 05:06:33PM +0800, Chao Yu wrote:
> Hi,
> 
> I don't see any problem here, thanks for your report. :)
> 
> Thanks,

What about if max_depth == 0 in __f2fs_find_entry()?  Then __f2fs_find_entry()
would return NULL without initializing *res_page.

A fix could be:

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 069f498af1e3..ceb4431b5669 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -357,16 +357,15 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
 	unsigned int max_depth;
 	unsigned int level;
 
+	*res_page = NULL;
+
 	if (f2fs_has_inline_dentry(dir)) {
-		*res_page = NULL;
 		de = f2fs_find_in_inline_dir(dir, fname, res_page);
 		goto out;
 	}
 
-	if (npages == 0) {
-		*res_page = NULL;
+	if (npages == 0)
 		goto out;
-	}
 
 	max_depth = F2FS_I(dir)->i_current_depth;
 	if (unlikely(max_depth > MAX_DIR_HASH_DEPTH)) {
@@ -377,7 +376,6 @@ struct f2fs_dir_entry *__f2fs_find_entry(struct inode *dir,
 	}
 
 	for (level = 0; level < max_depth; level++) {
-		*res_page = NULL;
 		de = find_in_level(dir, level, fname, res_page);
 		if (de || IS_ERR(*res_page))
 			break;