From ce3aba43599f0b50adbebff133df8d08a3d5fffe Mon Sep 17 00:00:00 2001
From: Anirudh Rayabharam <mail@anirudhrb.com>
Date: Fri, 7 May 2021 00:26:54 +0530
Subject: [PATCH] ext4: fix kernel infoleak via ext4_extent_header
Git-commit: ce3aba43599f0b50adbebff133df8d08a3d5fffe
Patch-mainline: v5.14-rc1
References: bsc#1189562 bsc#1196761 CVE-2022-0850

Initialize eh_generation of struct ext4_extent_header to prevent leaking
info to userspace. Fixes KMSAN kernel-infoleak bug reported by syzbot at:
http://syzkaller.appspot.com/bug?id=78e9ad0e6952a3ca16e8234724b2fa92d041b9b8

Cc: stable@kernel.org
Reported-by: syzbot+2dcfeaf8cb49b05e8f1a@syzkaller.appspotmail.com
Fixes: a86c61812637 ("[PATCH] ext3: add extent map support")
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Link: https://lore.kernel.org/r/20210506185655.7118-1-mail@anirudhrb.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/ext4/extents.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -853,6 +853,7 @@ int ext4_ext_tree_init(handle_t *handle,
 	eh->eh_entries = 0;
 	eh->eh_magic = EXT4_EXT_MAGIC;
 	eh->eh_max = cpu_to_le16(ext4_ext_space_root(inode, 0));
+	eh->eh_generation = 0;
 	ext4_mark_inode_dirty(handle, inode);
 	return 0;
 }
@@ -1107,6 +1108,7 @@ static int ext4_ext_split(handle_t *hand
 	neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
 	neh->eh_magic = EXT4_EXT_MAGIC;
 	neh->eh_depth = 0;
+	neh->eh_generation = 0;
 
 	/* move remainder of path[depth] to the new leaf */
 	if (unlikely(path[depth].p_hdr->eh_entries !=
@@ -1184,6 +1186,7 @@ static int ext4_ext_split(handle_t *hand
 		neh->eh_magic = EXT4_EXT_MAGIC;
 		neh->eh_max = cpu_to_le16(ext4_ext_space_block_idx(inode, 0));
 		neh->eh_depth = cpu_to_le16(depth - i);
+		neh->eh_generation = 0;
 		fidx = EXT_FIRST_INDEX(neh);
 		fidx->ei_block = border;
 		ext4_idx_store_pblock(fidx, oldblock);