Re: UBSAN: shift-out-of-bounds in ext4_fill_super

From: Dmitry Vyukov
Date: Thu Dec 10 2020 - 03:11:16 EST


On Thu, Dec 10, 2020 at 4:50 AM syzbot
<syzbot+345b75652b1d24227443@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot tried to test the proposed patch but the build/boot failed:
>
> failed to checkout kernel repo git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git on commit e360ba58d067a30a4e3e7d55ebdd919885a058d6: failed to run ["git" "fetch" "--tags" "d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8"]: exit status 1
> From git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
> * [new branch] bisect-test-ext4-035 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/bisect-test-ext4-035
> * [new branch] bisect-test-generic-307 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/bisect-test-generic-307
> * [new branch] dev -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/dev
> * [new branch] ext4-3.18 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-3.18
> * [new branch] ext4-4.1 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-4.1
> * [new branch] ext4-4.4 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-4.4
> * [new branch] ext4-4.9 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-4.9
> * [new branch] ext4-dax -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-dax
> * [new branch] ext4-tools -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/ext4-tools
> * [new branch] fix-bz-206443 -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/fix-bz-206443
> * [new branch] for-stable -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/for-stable
> * [new branch] fsverity -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/fsverity
> * [new branch] lazy_journal -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/lazy_journal
> * [new branch] master -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/master
> * [new branch] origin -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/origin
> * [new branch] pu -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/pu
> * [new branch] test -> d06f7b29746c7f0a52f349ff7fbf2a3f22d27cf8/test
> * [new tag] ext4-for-linus-5.8-rc1-2 -> ext4-for-linus-5.8-rc1-2
> ! [rejected] ext4_for_linus -> ext4_for_linus (would clobber existing tag)

Interesting. First time I see this. Should syzkaller use 'git fetch
--tags --force"?...
StackOverflow suggests it should help:
https://stackoverflow.com/questions/58031165/how-to-get-rid-of-would-clobber-existing-tag


> * [new tag] ext4_for_linus_bugfixes -> ext4_for_linus_bugfixes
> * [new tag] ext4_for_linus_cleanups -> ext4_for_linus_cleanups
> * [new tag] ext4_for_linus_fixes -> ext4_for_linus_fixes
> * [new tag] ext4_for_linus_fixes2 -> ext4_for_linus_fixes2
>
>
>
> Tested on:
>
> commit: [unknown
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git e360ba58d067a30a4e3e7d55ebdd919885a058d6
> dashboard link: https://syzkaller.appspot.com/bug?extid=345b75652b1d24227443
> compiler: gcc (GCC) 10.1.0-syz 20200507
> patch: https://syzkaller.appspot.com/x/patch.diff?x=1499c287500000