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b=zqloceJ2NnoaNE/z83IdujWffVPp8pbfyTibAAG0UTAIRpMMogdYsCLyWxAEbhWVf kEM95mtlRnyAiIK2/P28HpJrG1/JqtVkm3j225uxEhLMeJqsk3fnN+WEOST/EUFgbC 6CIUcYv03CtwRV33TShPygrqR12zpf3/4ymb8jr4= Date: Wed, 9 Sep 2026 00:13:41 -0700 From: Andrew Morton To: Anastasios Papagiannis Cc: linux-mm@kvack.org, liam@infradead.org, ljs@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Hajime Tazaki Subject: Re: [PATCH] mm/nommu: Reject wrapping ranges in access_remote_vm() Message-Id: <20260909001341.6a7c3556259f7cf9a79c1da7@linux-foundation.org> In-Reply-To: <20260909064231.18693-1-tasos.papagiannnis@gmail.com> References: <20260909064231.18693-1-tasos.papagiannnis@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-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A1E60C0006 X-Stat-Signature: e9txumqqc8sfedm99fxyb51qmuafs56g X-HE-Tag: 1788938022-47054 X-HE-Meta: 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 nuLHCucM 4tGDZN9kQ1csuKodSo+/4g1RwdLzHpIMcBve/QBrL7YPcGMNHKh4nzixrd6/HTzsLIq7XtgOMKP8BsX88i0+/AaoDfVbnfh/bVMhYcajSqMn00tKhjJlSNurobEFquvfrr9iPIRkz4lNoNMYG7RU/LvXYaLLt6+nAKXtDg0ruHj09/iCnx1m2aLyGNcKxxJ3SPDKCjciWiJrsWz0BaUhaCELZfgWuhnnnPFsmYfjDwyyOkzMyhaA1kLGU7ZYl0EW+pR/85GtbplB9LIHtwvt+ucWAEJPRZ7t7tFSiyDKSSWEWcIklCry4tr6q44dwzXa876zTUF+peJ0VcaDAKc1KFHIuhN4nukSO9Rkg0YI2/rCEoxwlH0nhskGVf/VVCdkNCQHQ7hqNk8G4CYkLX7rbwXN0uPRHE0VIcB9ZOFTYpqDMBKDyw/ULpct9FbXPdgcSbw391sK+9AofleDSyNOH+x3JOpPkoFwJxVTb Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 9 Sep 2026 09:42:31 +0300 Anastasios Papagiannis wrote: > The NOMMU implementation of access_process_vm() rejects address ranges > whose end wraps around, but access_remote_vm() bypasses this check even > though both functions delegate to __access_remote_vm(). > > Move the wraparound check into __access_remote_vm() so it applies to > both entry points. lgtm, thanks. > This is originally reported in [1]. > > [1] https://lore.kernel.org/bpf/4ef240a5bea36ff84df9589671367832860795159386a4c8fba546a0fa8b786f@mail.kernel.org/ Ah, bpfbot scored one. Sashiko might have found more issues in there: https://sashiko.dev/#/patchset/20260909064231.18693-1-tasos.papagiannnis@gmail.com I'll optimistically cc Hajime Tazaki, who has been doing some NOMMU work recently. > Fixes: f55f199b7d76 ("NOMMU: implement access_remote_vm") > Signed-off-by: Anastasios Papagiannis > --- > mm/nommu.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/nommu.c b/mm/nommu.c > index 498e01ee40b0..ed44510e3770 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -1674,6 +1674,9 @@ static int __access_remote_vm(struct mm_struct *mm, unsigned long addr, > struct vm_area_struct *vma; > int write = gup_flags & FOLL_WRITE; > > + if (addr + len < addr) > + return 0; > + > if (mmap_read_lock_killable(mm)) > return 0; > > @@ -1727,9 +1730,6 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in > { > struct mm_struct *mm; > > - if (addr + len < addr) > - return 0; > - > mm = get_task_mm(tsk); > if (!mm) > return 0; >