From: Andrew Morton <akpm@linux-foundation.org>
To: Hajime Tazaki <thehajime@gmail.com>
Cc: liam@infradead.org, ljs@kernel.org, vbabka@kernel.org,
jannh@google.com, pfalcato@suse.de, linux-mm@kvack.org,
geert@linux-m68k.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: nommu: free unused resources when mremap shrinks the vma
Date: Fri, 10 Jul 2026 17:43:40 -0700 [thread overview]
Message-ID: <20260710174340.9f3b420629769b556f44640f@linux-foundation.org> (raw)
In-Reply-To: <20260710021028.892645-1-thehajime@gmail.com>
On Fri, 10 Jul 2026 11:10:28 +0900 Hajime Tazaki <thehajime@gmail.com> wrote:
> When shrinking a VMA via mremap, the bounds are modified directly:
> mm/nommu.c:do_mremap() {
> ...
> vma->vm_end = vma->vm_start + new_len;
> ...
> }
> This shrink the VMA without updating its bounds in the maple tree.
> If the maple tree (mm->mm_mt) still contains the old bounds, a user
> process could access the freed portion. The stale maple tree would
> incorrectly return the shrunk VMA for an address past its new vm_end.
>
> This commit fixes this issue by calling vmi_shrink_vma() when shrink
> happens.
Thanks again for helping with NOMMU. I'd like to give you a medal, but
you'll have to settle for an overstuffed inbox.
Sashiko is up to its usual tricks:
https://sashiko.dev/#/patchset/20260710021028.892645-1-thehajime@gmail.com
I assume that ENOMEM is more likely on NOMMU, and that we should hence be
more defensive about handling it. Seems we have not been.
next prev parent reply other threads:[~2026-07-11 0:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-10 2:10 [PATCH] mm: nommu: free unused resources when mremap shrinks the vma Hajime Tazaki
2026-07-11 0:43 ` Andrew Morton [this message]
2026-07-11 3:03 ` Hajime Tazaki
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