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Subject: [PATCH] hfsplus: fix uninit-value in hfsplus_strcasecmp
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Syzbot reported a KMSAN uninit-value issue in hfsplus_strcasecmp() during
filesystem mount operations. The root cause is that hfsplus_find_cat()
declares a local hfsplus_cat_entry variable without initialization before
passing it to hfs_brec_read().

If hfs_brec_read() doesn't completely fill the entire structure (e.g., when
the on-disk data is shorter than sizeof(hfsplus_cat_entry)), the padding
bytes in tmp.thread.nodeName remain uninitialized. These uninitialized
bytes are then copied by hfsplus_cat_build_key_uni() into the search key,
and subsequently accessed by hfsplus_strcasecmp() during catalog lookups,
triggering the KMSAN warning.

Fix this by zeroing the tmp variable before use to ensure all padding
bytes are initialized.

Reported-by: syzbot+d80abb5b890d39261e72@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d80abb5b890d39261e72
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/hfsplus/catalog.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/hfsplus/catalog.c b/fs/hfsplus/catalog.c
index 02c1eee4a4b8..9c75d1736427 100644
--- a/fs/hfsplus/catalog.c
+++ b/fs/hfsplus/catalog.c
@@ -199,6 +199,7 @@ int hfsplus_find_cat(struct super_block *sb, u32 cnid,
 	u16 type;
 
 	hfsplus_cat_build_key_with_cnid(sb, fd->search_key, cnid);
+	memset(&tmp, 0, sizeof(tmp));
 	err = hfs_brec_read(fd, &tmp, sizeof(hfsplus_cat_entry));
 	if (err)
 		return err;
-- 
2.43.0