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s=korg; t=1755093235; bh=cb6IHvKJI6s9a7NefYpZ8pOVcYdWMtHhY4ST4nI1r9o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mCPLqBCSonSc1PNeIvJP/EqqsgjspL0NafTpNdgQPnaWvE+58pv1tAJIxRQFCqssg fsmFmez2PBUkvRpKyzO3qstcs7257EdUEUwtOG/D9v50oaSbwpUPsxgceky8bhOziJ LAcRHaYPuhwABBEmpo24LwWWfyqXdq2hKPRbw6eA= Date: Wed, 13 Aug 2025 15:53:51 +0200 From: Greg KH To: Pasha Tatashin Cc: Pratyush Yadav , Jason Gunthorpe , Vipin Sharma , jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, rppt@kernel.org, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com Subject: Re: [PATCH v3 29/30] luo: allow preserving memfd Message-ID: <2025081341-essence-unheard-63a1@gregkh> References: <20250807014442.3829950-1-pasha.tatashin@soleen.com> <20250807014442.3829950-30-pasha.tatashin@soleen.com> <20250813063407.GA3182745.vipinsh@google.com> <2025081310-custodian-ashamed-3104@gregkh> <2025081351-tinsel-sprinkler-af77@gregkh> <20250813124140.GA699432@nvidia.com> <2025081334-rotten-visible-517a@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B2A694001A X-Stat-Signature: e9zqehhbawbobpgjcsssix3uwdkzo6o6 X-Rspam-User: X-HE-Tag: 1755093236-976257 X-HE-Meta: U2FsdGVkX1+hdYYSAkhLm8SuF7POhw205T40Th7GK8wzwb1zpR8z0bQmTxxIBLuTIZwOSQhdjfty7hmgy9gLZkkAVtjKOi1s07/pxg2L+nicTry8GdWWdi4e0p0L2eafe7RhmMgFi3u3oUthKOumBoAi05fdqjKNCEbewyk26TpWVuojS59RkrRHHh/RcmHK8npM5zi1/f/4YnHxtzgs+8gttIJ32IAB4/LYE2UEsx2IRPFenG5aUiW4D8uSNcS7nFxRIRyBT5LtSUSTH2gTeg3zpR0HlqQzvKQCWADF0T243uIlA1U9bBBeVjovv7y6qs/F2si66ZuMyx27MIT3dOQBrjVtisdqQnCXiKty/tdY5U+/G9pqMe7RwqUlO3eSuRg+kWfezhFDJpkvG37n6RWjsof3dyMOVb8tT7RqYAo3VD2zHt9NAT89Plgt7GvTqVH5n4oofbE6J7oJ/zCMJAdfaORg53soufQf6O9Hhys0+JnINnlW57biYgL8dlYv7CBOfEmowzpIACXR4OUJ7hzEkypnsu/nlYhMBwhOscGpTM1ltUivQLn5ohoeAt+7FRs4KkF9UUr0bRWfGwL4tso2yb6M4PWBk8zD/rJI4IkTABvyUtcfG8Zd1aG0LEptT0bTIjh+QIL5rA6XR/aqNFrSYHx7QXM+5TplJJv7LD/YKIWKF/KV3Uxprf6uFL1BV9vhjU/woDzYmhhXOM/19vjh6nWGKyScQY52thVqCKUYQ6myzMZG8Fh6sJAPJFZTijey++NTKGOXxpsQ3SmwLJI2DHbH2dE3dFdMspn4KCIK45ApOYyvu+TYhYvqaDOND9LxmTtTTRSXGWYpi86vgNFYmDTFAxjuu3vW8rHWGts6Lbv1W2CNS7zAWGRp+GPDsV7xLiZA82e7dywcgYEHO4+um9/bjB7+/aQatPCKUgOTG6tCkVwlVIy9wMdyioncHAT17qPdwFkkh7zVhSR wjkOHoaC nXdhOLwDd5WEPtq/J4aVApJMMHW5YD1uzciMij/i3i5BOvAoiIF9qmMAYkhXWk9FFz7OAaFOUIATdTlEHPL46RgUKHtQdYLMOhBqN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 13, 2025 at 01:41:51PM +0000, Pasha Tatashin wrote: > On Wed, Aug 13, 2025 at 1:37 PM Pratyush Yadav wrote: > > > > On Wed, Aug 13 2025, Greg KH wrote: > > > > > On Wed, Aug 13, 2025 at 09:41:40AM -0300, Jason Gunthorpe wrote: > > [...] > > >> Use the warn ons. Make sure they can't be triggered by userspace. Use > > >> them to detect corruption/malfunction in the kernel. > > >> > > >> In this case if kho_unpreserve_folio() fails in this call chain it > > >> means some error unwind is wrongly happening out of sequence, and we > > >> are now forced to leak memory. Unwind is not something that userspace > > >> should be controlling, so of course we want a WARN_ON here. > > > > > > "should be" is the key here. And it's not obvious from this patch if > > > that's true or not, which is why I mentioned it. > > > > > > I will keep bringing this up, given the HUGE number of CVEs I keep > > > assigning each week for when userspace hits WARN_ON() calls until that > > > flow starts to die out either because we don't keep adding new calls, OR > > > we finally fix them all. Both would be good... > > > > Out of curiosity, why is hitting a WARN_ON() considered a vulnerability? > > I'd guess one reason is overwhelming system console which can cause a > > denial of service, but what about WARN_ON_ONCE() or WARN_RATELIMIT()? > > My understanding that it is vulnerability only if it can be triggered > from userspace, otherwise it is a preferred method to give a notice > that something is very wrong. > > Given the large number of machines that have panic_on_warn, a reliable > kernel crash that is triggered from userspace is a vulnerability(?). Yes, and so is a unreliable one :)