linux-kernel - Re: [syzbot] general protection fault in vma_interval_tree

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Message-ID: <20220519020341.rr3s6b4dr7o36cqb@revolver>
Date:   Thu, 19 May 2022 02:03:53 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        syzbot <syzbot+ee1fdd8dcc770a3a169a@...kaller.appspotmail.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        Michel Lespinasse <michel@...pinasse.org>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>
Subject: Re: [syzbot] general protection fault in vma_interval_tree_remove

* Liam R. Howlett <Liam.Howlett@...cle.com> [220516 13:59]:
> * Andrew Morton <akpm@...ux-foundation.org> [220514 16:50]:
> > On Sat, 14 May 2022 13:18:26 -0700 syzbot <syzbot+ee1fdd8dcc770a3a169a@...kaller.appspotmail.com> wrote:
> > 
> > > syzbot has found a reproducer for the following issue on:
> > > 
> > > HEAD commit:    1e1b28b936ae Add linux-next specific files for 20220513
> > > git tree:       linux-next
> > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=11da21b9f00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e4eb3c0c4b289571
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=ee1fdd8dcc770a3a169a
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=142757f1f00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17cf0966f00000
> > 
> > Thanks.
> > 
> > So it was there on April 28 and it's there now.  Liam, do you think
> > anything in the mapletree changes could have perturbed the interval
> > tree handling?
> 
> It is certainly possible, these two trees are intertwined so much.  One
> area that sticks out as a possibility is vma_expand().  I created a
> vma_expand() function to handle growing a vma and potentially removing
> the next vma.  I do some interval tree modifications in there.
> 
> I'll add it to my list of items to look at.

This was my bug.  I reused a pointer that wasn't reused in this function
until I altered the error path in this commit.

Please apply this patch to the maple tree series to fix "mm/mmap: use
advanced maple tree API for mmap_region()"

Thanks,
Liam

View attachment "0001-mm-mmap-Fix-advanced-maple-tree-API-for-mmap_region.patch" of type "text/x-diff" (2000 bytes)