linux-kernel - Re: UBSAN: shift-out-of-bounds in ext4_fill

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Message-ID: <CACT4Y+bkaVq1RzONGuPJxu-pSyCSRrEs7xV0sa2n0oLNkicHQQ@mail.gmail.com>
Date:   Thu, 10 Dec 2020 09:09:51 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+345b75652b1d24227443@...kaller.appspotmail.com>
Cc:     Andreas Dilger <adilger.kernel@...ger.ca>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        linux-ext4@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        "Theodore Ts'o" <tytso@....edu>
Subject: Re: UBSAN: shift-out-of-bounds in ext4_fill_super

On Thu, Dec 10, 2020 at 4:50 AM syzbot
<syzbot+345b75652b1d24227443@...kaller.appspotmail.com> 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