From: Andrew Morton <akpm@linux-foundation.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>,
dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
syzbot+a504cb5bae4fe117ba94@syzkaller.appspotmail.com,
Steve Sistare <steven.sistare@oracle.com>,
Muchun Song <muchun.song@linux.dev>,
David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH] mm/hugetlb: Don't crash when allocating a folio if there are no resv
Date: Wed, 18 Jun 2025 17:02:48 -0700 [thread overview]
Message-ID: <20250618170248.89ff5c3d3fe23233424fd4da@linux-foundation.org> (raw)
In-Reply-To: <99b9f7c8-62e0-4500-b4f1-0efdb73bf502@arm.com>
On Wed, 18 Jun 2025 12:14:49 +0530 Anshuman Khandual <anshuman.khandual@arm.com> wrote:
> > Therefore, prevent the above crash by replacing the VM_BUG_ON()
> > with WARN_ON_ONCE() as there is no need to crash the system in
> > this situation and instead we could just warn and fail the
> > allocation.
>
> Why there are no reserved huge pages in such situations and also how
> likely this might happen ? Is it recoverable ?
I'm suspecting we don't know.
> >
> > Fixes: 26a8ea80929c ("mm/hugetlb: fix memfd_pin_folios resv_huge_pages leak")
How was this arrived at? This is merely the patch which added the assertion.
> > Reported-by: syzbot+a504cb5bae4fe117ba94@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=a504cb5bae4fe117ba94
I can't find any mailing report/discussion of this. The Closes: takes
us to the syskaller report which is a bit of a dead end.
I agree with the patch - converting a BUG into a WARN+recover is a good
thing but as far as I can tell, we don't know what's causing this
situation.
syskaller has a C reproducer, if anyone is feeling brave.
next prev parent reply other threads:[~2025-06-19 0:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-18 5:28 [PATCH] mm/hugetlb: Don't crash when allocating a folio if there are no resv Vivek Kasireddy
2025-06-18 6:44 ` Anshuman Khandual
2025-06-19 0:02 ` Andrew Morton [this message]
2025-06-19 5:30 ` Kasireddy, Vivek
2025-06-23 23:35 ` Andrew Morton
2025-06-25 14:18 ` Kasireddy, Vivek
2025-06-25 20:46 ` Andrew Morton
2025-06-19 13:53 ` Oscar Salvador
2025-06-21 2:02 ` Kasireddy, Vivek
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