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b=a/uR9vXhx9AxJeRoIXw2P+Xo6eJbkLGU0etqDWBpGV6MBGmZwlfcngoU3R65Wk3WS bd8L7pSd2vcI1dis8rUXnt4RbrloYsbagJ+yfzBE7KCHCp3er4QWjxUiX6Hn3pwmEW UqN4/BCOWololLqxWTfKi5vfkHJjQJ4h4N6A2mArBTp4v8vQlwCyCfl7KPFLOD95IA fOE5cVENbX9+0ZBd8PGw6PXoFkC3errgcJRbeWIAdb5wEk8hWH+D3ikmwjuHONzroA 9X6snFPs4dIFUezVArlndAMhAtJRvm3s0VkU6oNc+KQmmxw5Y+Bv3mp2Tw4IhBy+Rd g44fFDKG+cCEA== Date: Fri, 25 Sep 2026 14:20:33 +0100 From: "Lorenzo Stoakes (ARM)" To: Anastasios Papagiannis Cc: linux-mm@kvack.org, akpm@linux-foundation.org, liam@infradead.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/nommu: Reject wrapping ranges in access_remote_vm() Message-ID: References: <20260909064231.18693-1-tasos.papagiannnis@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260909064231.18693-1-tasos.papagiannnis@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: AA6BA10000E X-Stat-Signature: 8sm7ztqsrb8rkmayhf1578wubzsh1n1o X-HE-Tag: 1790342438-199427 X-HE-Meta: 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 aW1bAJ+M 9soiI+frstnkQCqrl7F00+fHLXdC9kJ+Wp790kOWOKJZ5uQWjaD4ONF/4iDobYv1niKxMfpgSK8hEDTsrF5PMcWTGQdBO2gSh3QKegg9TE542iX4eCs6gvhOh8/mkZsAO9qXxKvQ8uTvAyG9Cwd7Zv3UfxaI2y4jATlBicL9ODJr8uDZMbTJtG+vglbU1gPR9Uu8oPyXDBNsXtd8cBmPBYi25MzuPfWjbRLe5jBc04HLME4ufVjrBvoFzUFwoAMDX+EOqHLQHSUINnj1RFvz0LdmoQNR8gqcdV7zwc3ms6A0VAOa5S5fpWL5RPz/VYAGa8VnFf2lcChnMRQLMndittW5kM6ul+vlMCTxPHBHADPzzfVugRSkdotB1e8i7EMzTCJQFr4+rIJESL3MDIe0NVp7oON+4KEm1FSxe Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: BTW always feel free to nag if you're not getting review! Something things get missed. (Though I'd say wait at least a couple weeks before doing that!) On Wed, Sep 09, 2026 at 09:42:31AM +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. > > This is originally reported in [1]. > > [1] https://lore.kernel.org/bpf/4ef240a5bea36ff84df9589671367832860795159386a4c8fba546a0fa8b786f@mail.kernel.org/ Probably better to drop this big and make this a Link: tag. > > Fixes: f55f199b7d76 ("NOMMU: implement access_remote_vm") Cc: stable I think? > Signed-off-by: Anastasios Papagiannis Seems reasonable to me! So: Reviewed-by: Lorenzo Stoakes (ARM) > --- > 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; > > base-commit: 0d9ff90a5422cc7509258aaaba1e7481df4d332a > -- > 2.55.0 > -- Cheers, Lorenzo