From: Roman Kagan <rkagan@virtuozzo.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Matthew Wilcox" <mawilcox@microsoft.com>,
syzbot <syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"KVM list" <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"the arch/x86 maintainers" <x86@kernel.org>,
"Cathy Avery" <cavery@redhat.com>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] idr: fix invalid ptr dereference on item delete
Date: Fri, 11 May 2018 08:57:04 +0300 [thread overview]
Message-ID: <20180511055704.GB12563@rkaganip.lan> (raw)
In-Reply-To: <CACT4Y+bZaW6NN-RdVd+EL1pXQs42Nb-dWUn733=eEORT_3NjUA@mail.gmail.com>
On Fri, May 11, 2018 at 07:40:26AM +0200, Dmitry Vyukov wrote:
> On Fri, May 11, 2018 at 1:54 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> > On 10/05/2018 21:16, Roman Kagan wrote:
> >> If an IDR contains a single entry at index==0, the underlying radix tree
> >> has a single item in its root node, in which case
> >> __radix_tree_lookup(index!=0) doesn't set its *@nodep argument (in
> >> addition to returning NULL).
> >>
> >> However, the tree itself is not empty, i.e. the tree root doesn't have
> >> IDR_FREE tag.
> >>
> >> As a result, on an attempt to remove an index!=0 entry from such an IDR,
> >> radix_tree_delete_item doesn't return early and calls
> >> __radix_tree_delete with invalid parameters which are then dereferenced.
> >>
> >> Reported-by: syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com
> >> Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
> >> ---
> >> lib/radix-tree.c | 5 +++--
> >> 1 file changed, 3 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/lib/radix-tree.c b/lib/radix-tree.c
> >> index da9e10c827df..10ff1bfae952 100644
> >> --- a/lib/radix-tree.c
> >> +++ b/lib/radix-tree.c
> >> @@ -2040,8 +2040,9 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
> >> void *entry;
> >>
> >> entry = __radix_tree_lookup(root, index, &node, &slot);
> >> - if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
> >> - get_slot_offset(node, slot))))
> >> + if (!entry && (!is_idr(root) || !node ||
> >> + node_tag_get(root, node, IDR_FREE,
> >> + get_slot_offset(node, slot))))
> >> return NULL;
> >>
> >> if (item && entry != item)
> >>
> >
> > I cannot really vouch for the patch, but if it is correct it's
> > definitely stuff for stable. The KVM testcase is only for 4.17-rc but
> > this is a really nasty bug in a core data structure.
> >
> > Cc: stable@vger.kernel.org
> >
> > Should radix-tree be compilable in userspace, so that we can add unit
> > tests for it?...
>
> Good point.
>
> For my education, what/where are the tests that run as user-space code?
Actually there are userspace tests for it under tools/tests/radix-tree,
but I didn't manage to get them to build. Looks like the recent
introduction of a spin_lock in the radix_tree structure (for XArray
work?) broke them.
Roman.
next prev parent reply other threads:[~2018-05-11 5:57 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-10 19:16 [PATCH] idr: fix invalid ptr dereference on item delete Roman Kagan
2018-05-10 23:54 ` Paolo Bonzini
2018-05-11 5:40 ` Dmitry Vyukov
2018-05-11 5:57 ` Roman Kagan [this message]
2018-05-11 9:12 ` Paolo Bonzini
2018-05-18 20:29 ` Roman Kagan
2018-05-18 17:50 Matthew Wilcox
2018-05-18 20:23 ` Roman Kagan
2018-05-19 0:31 ` Matthew Wilcox
2018-05-18 22:31 ` Andrew Morton
2018-05-19 0:28 ` Matthew Wilcox
2018-05-19 6:26 ` Roman Kagan
2018-05-19 14:14 ` Matthew Wilcox
2018-05-21 19:13 ` Andrew Morton
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