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Fri, 01 May 2026 12:38:35 -0700 (PDT) Date: Fri, 1 May 2026 19:38:34 +0000 From: Pasha Tatashin To: David CARLIER Cc: Pasha Tatashin , akpm@linux-foundation.org, pratyush@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/memfd_luo: reject memfds whose page count exceeds UINT_MAX Message-ID: References: <20260423125648.152113-1-devnexen@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On 05-01 20:26, David CARLIER wrote: > On 2026-05-01 18:59, Pasha Tatashin wrote: > > I think, the fix should be first done at memfd_pin_folios() to > change > > max_folios to 'long' or 'unsigned long', and then just updated > > memfd_luo.c to match. > > Even with memfd_pin_folios() widened, memfd_luo_preserve_folios() > still > kvmalloc_objs()s the folios array up front -- at UINT_MAX entries > that's > already ~32 GiB of pointer array, which won't realistically succeed. > So > the guard here still makes sense, just on allocation grounds rather than > interface truncation. > > Happy to widen memfd_pin_folios() as a separate patch, but I'd keep > the > -EFBIG check regardless. Or did you have a different shape in mind? Ah, Good point about kvmalloc_objs(), I am not against this, even though it is a very theoretical issue. Reviewed-by: Pasha Tatashin