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b=Bt0/BvUxbtZOGR9BnfwlJwap/0GQ8fHT1MZ9VGpIu0afakcvrOaFjGwt5JLkDhW/7 2Euz7Z3ngnsUmpKO5aSIs4xOgtemWJ6hb2Znyblf06uxfAJ2en3cY2WQbAwWjFhsyQ Q1Z2slFaS8g8rOHPuXuXa9DGrhQyJ/yrbicPHS1o= Date: Fri, 10 Jul 2026 17:43:40 -0700 From: Andrew Morton To: Hajime Tazaki 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 Message-Id: <20260710174340.9f3b420629769b556f44640f@linux-foundation.org> In-Reply-To: <20260710021028.892645-1-thehajime@gmail.com> References: <20260710021028.892645-1-thehajime@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: e3dxbk6qem3riozdwsffsb88iqfxr73u X-Rspamd-Queue-Id: 51420C0004 X-Rspamd-Server: rspam01 X-Rspam-User: X-HE-Tag: 1783730622-246916 X-HE-Meta: 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 N00n4OpI b+yLethJ6qgp2IiLpgTqxXX1xDX0l485Ojhyc0CEwBM211oXRpUIraqrxupMhdT9n5WIOoESh49xKc8YjVRoILGs+NKnaCimvV6iBBn98SIdldRkkpFsnM/GbXec+dlgqbk28QcTxbz68dPZP9BR/+DwcaX4DmVzj1Om7JCeVIBeuc8zZc2BlSXNDPl3xz01yKgJo0b0TcZNo6OhoICFKccS1LQdACBZ65MssZhX8EVZF4O/yaIiW3hqFcQq+29pTzrNsiNWrc4jbDrG+kshnpNzk8/WHS2h6Ns7knNkQsmJ7kY+YsqlMrLGWDPFKEaX025iXHlIWWwOj+0vwQS0wtVBptJjGmS0LWANCOrJ+MapHCdU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 10 Jul 2026 11:10:28 +0900 Hajime Tazaki 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.