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Mon, 22 Dec 2025 15:38:32 -0800 (PST) MIME-Version: 1.0 References: <20251222141817.13335-1-klourencodev@gmail.com> <20251222095248.18c4c102abcc8fb4f61c7067@linux-foundation.org> In-Reply-To: <20251222095248.18c4c102abcc8fb4f61c7067@linux-foundation.org> From: Kevin Lourenco Date: Tue, 23 Dec 2025 00:38:21 +0100 X-Gm-Features: AQt7F2qsDhp4u5LV9CR2xD6WKD4jJMPjz1DHUTwwJF1Z2YzR1yZB3JEJJCcbL58 Message-ID: Subject: Re: [PATCH] mm/fadvise: validate offset in generic_fadvise To: Andrew Morton Cc: linux-mm@kvack.org, david@kernel.org, Kevin Lourenco Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 531421C000A X-Stat-Signature: ng6mat5xs7mqbyekakxrfjojtsend8a9 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1766446714-840581 X-HE-Meta: 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 r6pCgmoS NSf2oolQnws9Md3VD4pqTzt7GupNq/tbUSQz/TOOlSzkAWQMnCmkdRMFwFUf7okjmvAQy2J9UFYjEE8HqG5NkrAwjVHaBZ2kUmO5nnUWCUQ3hAkachtSpm/BN08ndaiidgaWZUD1sP7FJt8mgKluDROh0JABZ/2DQgjQhO+x0eZ58WLTI2D/5p/J0ZB9rRPR3jWXFul9p5/BEmlZM5w9uohxG6a0aOOp2Y5/F618Y20CzylmHUgBKtYAE/AYTp2SRaudnSqhH7Yy6Pr7gSZJ1tJcDbMaR/3S0s6z6I+sHT5GfLMlrEKI1j9gflabQEHqIN5kMDrASbiGcWvk00NJNJsf8llnzgQf+sx8DapOaBoYoBsf2NeekD6VL7rTJVdnRB7S3BU1QlN7QlsnnWJxFy2J7SS7tccsnACGfYLzVfNUNdLiLtx4yjtMVKz+0MkxQahVTMLraW5X0V9hEyo8b1ajl9Rp8PQ1olLEU+5CyteSPk2vqKmIZ9ntwiD1/+nxBBLcKSp87sDI3V+jZWsTfo49L0rCFnc3M61a3wCcHegT7xl465btD9NEX5/2HDrMFIQwc X-Bogosity: Ham, tests=bogofilter, spamicity=0.000143, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thank you, Andrew, for taking a look and for queueing in -next. I'll keep an eye on it and will adjust the patch if needed. Kevin Le lun. 22 d=C3=A9c. 2025 =C3=A0 18:52, Andrew Morton a =C3=A9crit : > > On Mon, 22 Dec 2025 15:18:17 +0100 klourencodev@gmail.com wrote: > > > From: Kevin Lourenco > > > > When converted to (u64) for page calculations, a negative offset > > can produce extremely large page indices. This may lead to issues in ce= rtain advice modes (excessive readahead or > > cache invalidation) > > > > offsets are normally non-negative, but the API does not guarantee this.= Since 'len' is already > > validated, checking 'offset' here is reasonable to prevent potential sy= stem instability. > > > > Yeah, seems this code really didn't think about negative offsets. > > fadvise(fd, -20, 40, advice); > > does make some sense I guess - equivalent to > > fadvise(fd, 0, 20, advice); > > but whether this is how the implementation actually treats -20,40 is > unclear. Probably not, and what will filemap_flush_range() make of > this. > > ugh. > > I suppose I'll toss this into -next for now, see if it breaks any tests. > But more thought is needed. >