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AJvYcCVtpVZBJz8hmwGNPa0U9BrU4/a90HGtt2E5si6irgagj+9WqYT35/i0MXFtlUvQb9Xo4MjUKzkQ4w==@kvack.org X-Gm-Message-State: AOJu0YxNnvDgRL2/epEIXdaDlzqwGmvnpPKTl1ogyxGRN/aHB1jn2w1G P1FcVtG4SikuFdxwBcf3MLv/LihaOE5C1kb8tHxfDIDKWhrEN8qzk++irMswrCmH1bFAuLrYVd6 j5A/UhtRpA2MzoYnnNx7UQPHn25u/vzk= X-Gm-Gg: ASbGncuYcAEnd1V2880VNKOVKM3tLUi84a/WTin1fIQhsMEi+h68Swya51OxUcGNn7l iBoitB1JJ9Zje8IuGAvBBWIfuQA722c3JXD77Q0qtB/gJvZcTUJjeTCvak9vQnRFsrPNen9R2W7 VYiu9q1LEgPksF2g+I6Fp18Bg8bCeQYmtO26FIutF+b+Sf431Q1pQnWLBr+Zs3awQX+8xTN/g3J ih0coElTh0sgiG5bo6kmwcaoAS0gC1ouSdrFo0D X-Google-Smtp-Source: AGHT+IHe94eMIWMY4dbrxy1YiHjHy0HuBEp+5ADPw2mSy4ygzqofX4QZ6gFssRpbt5INRd/s9w0eUBJOOA9RRs/hVCY= X-Received: by 2002:a05:622a:592:b0:4b2:9830:197 with SMTP id d75a77b69052e-4b31da3cdadmr39861351cf.48.1756610223300; Sat, 30 Aug 2025 20:17:03 -0700 (PDT) MIME-Version: 1.0 References: <20250826071948.2618-1-laoar.shao@gmail.com> <20250826071948.2618-5-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Sun, 31 Aug 2025 11:16:27 +0800 X-Gm-Features: Ac12FXzUXlC_rm_aYklaAinmwNAfHTa64DZQJN2Q1d5F2Z14aWeMQl-5B-4ZRZM Message-ID: Subject: Re: [PATCH v6 mm-new 04/10] bpf: mark vma->vm_mm as trusted To: Lorenzo Stoakes Cc: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 44899140003 X-Stat-Signature: isuz6ca8o5xs9yy8mty7rba1693fw53g X-Rspam-User: X-HE-Tag: 1756610224-247184 X-HE-Meta: U2FsdGVkX1/dPBqjirYb70yBXU5h5ZglVMVJMKk7h0YGco31hJAGkieJJQ6ZGtgeJ8yGV4t3Iim7y+muCloXwM1LLu16fBeoTK4x0YifTk/1TY2CHWL+Cm+V2etw3okMiOZ5TawrPf63ZzuCH8QY5G51yCc+8XkgkM26O8j2JUUE5muTfs9qZhOD5flStm5FdSt6NfnBdrIU0vmV5IcusHv/N93KvKi2KtyIjW2vs4TFkJu/Uk2qND2V8HAxLAb0td9lZkPCGc/hEg9r2gS0teDNr0jT3MkHyFD7LGpHDm+5daCSxVFbAicEAjZg1yb9YL1Nngn1cgPEfwXJXp/u7Qw5FH4YwomDg7BvtihprY0CjsfCtEJA5rv5CjkY/e9Enuw7ZVzVuLQakLd5c0kzWLXf+yKk0ijVShOn65H68Ux6ONr5G0+0+HWBnZDCnM90//BYIbGAcCCr4p6cOXLS9TUZioAS6ov9LfA0m4sTXUiGeZhuIt6s1euRX+4h7xZkXUKE+S7z4XQKOsXq6s2uezJWYZ7e1AL14NqDQRWB549RHfIB2RDL6WTfULbpPIhaCYI9e+pMwNFvP0lO6x39qSk3QbrLX6G3c1GNz7cq5kNFraw88S7eFqXr43/vQrzvSDzWZm6c2Kcn0eEdePn5bpX4buRmQjdO7cJ6iH63XrCrZBUvdzfNMmg3ErwMFwxz307OZyU0kOUqfw5b0rG8hrtURF/u6h2Q6epKGgnSS1gXYqHKs4bxCSxU8K9ey1QRKWEGjXqiYqeSoXIuRyygfNga9OWi8khwH2scfIAP+AEW/rRsoMoXLmtPG+oBo/FL9TAygeEZqZjQyn52SY0lXOSCYhLjMkbk/+6MveWCxpASd7hHBfM0na6DYlSPRqUCnUv005HE/TpYhHLHMDbTZOPRzwS7zXykbJOGGjFX6f1drpaMIjzhDmol8HAeF2aKETYmomXXrNCLQnH7FSi ToJp7V4/ Bv/7muKX8YRn4FKJQUF38LHKfQuyNUCYHrlZ+6Zyg4whx26I0IcMAIsnbfnxfXQNfKSJjesz0XjDuT6d+aV4cWMFVvwPaIYqNK1FB 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 Fri, Aug 29, 2025 at 6:49=E2=80=AFPM Lorenzo Stoakes wrote: > > On Fri, Aug 29, 2025 at 11:05:01AM +0800, Yafang Shao wrote: > > On Thu, Aug 28, 2025 at 7:11=E2=80=AFPM Lorenzo Stoakes > > wrote: > > > > > > On Thu, Aug 28, 2025 at 02:12:12PM +0800, Yafang Shao wrote: > > > > On Wed, Aug 27, 2025 at 11:46=E2=80=AFPM Lorenzo Stoakes > > > > wrote: > > > > > > > > > > On Tue, Aug 26, 2025 at 03:19:42PM +0800, Yafang Shao wrote: > > > > > > Every VMA must have an associated mm_struct, and it is safe to = access > > > > > > > > > > Err this isn't true? Pretty sure special VMAs don't have that set= . > > > > > > > > I=E2=80=99m not aware of any VMA that doesn=E2=80=99t belong to an = mm_struct. If there > > > > is such a case, it would be helpful if you could point it out. In a= ny > > > > case, I=E2=80=99ll remove the VMA-related code in the next version = since it=E2=80=99s > > > > unnecessary. > > > > > > If you lok at get_vma_name() in fs/proc/task_mmu.c you'll see: > > > > > > if (!vma->vm_mm) { > > > *name =3D "[vdso]"; > > > return; > > > } > > > > > > So a VDSO will have this condition. > > > > > > I did a quick drgn()/printk() test and didn't see any, but maybe my s= ystem - but > > > in any case this appears to be a valid situation that can arise, pres= umably > > > because it's a VMA somehow shared with multiple mm's or something tru= ly god > > > awful like that :) > > > > Thanks for clarifying that. > > No problem! These weird edge cases are... weird and hugely confusing. I s= hould > document some of this somewhere, as it's at the moment more 'oh yeah I > remember...' then having to dig through to figure it out. > > The "/dev/zero file-backed but actually anon if MAP_PRIVATE'd" is another= fun > unique case. It would be immensely helpful if you could document these cases. We truly appreciate your contribution and the time you've invested in this. --=20 Regards Yafang