linux-kernel - Re: [syzbot] KASAN: null-ptr-deref Read in __free

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1905446.yKVeVyVuyW@leap>
Date:   Mon, 21 Mar 2022 09:50:05 +0100
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     syzbot <syzbot+d55757faa9b80590767b@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com
Cc:     dhowells@...hat.com, christophe.jaillet@...adoo.fr,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        David Howells <dhowells@...hat.com>
Subject: Re: [syzbot] KASAN: null-ptr-deref Read in __free_pages

On lunedì 21 marzo 2022 09:24:22 CET David Howells wrote:
> It should be possible to just test for the pointer being NULL in the loop
> before calling __free_pages() since the list was allocated with kcalloc().
> 
> David
> 
> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git 6d39b096627f0a1eb6e14f049d8ae3c93e0290f2
> 
> -- 
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@...glegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/970502.1647851062%40warthog.procyon.org.uk.
> 
This way you are doing two test for each iteration of the loop that calls
__free_pages(). One for the index "i" to stay less that an unnecessary 
high limit, the other for pages[i] being NULL.

However, since you are the Maintainer, yours are the rules :)

Regards,

Fabio M. De Francesco