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    Subject[PATCH 4.9 012/245] ext4: fix kernel infoleak via ext4_extent_header
    Date
    From: Anirudh Rayabharam <mail@anirudhrb.com>

    commit ce3aba43599f0b50adbebff133df8d08a3d5fffe upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

    --- a/fs/ext4/extents.c
    +++ b/fs/ext4/extents.c
    @@ -870,6 +870,7 @@ 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;
    }
    @@ -1126,6 +1127,7 @@ 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 !=
    @@ -1203,6 +1205,7 @@ 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);

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