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Tue, 10 Feb 2026 17:08:57 -0800 (PST) MIME-Version: 1.0 References: <20260209190605.1564597-1-avagin@google.com> <20260209190605.1564597-4-avagin@google.com> In-Reply-To: From: Andrei Vagin Date: Tue, 10 Feb 2026 17:08:46 -0800 X-Gm-Features: AZwV_QjzYmM-WZIpZJo7jxpdR0avYlD7_PH6H5p6BAaV9nV0wPBlcHA2v8Of8Jw Message-ID: Subject: Re: [PATCH 3/4] mm: synchronize saved_auxv access with arg_lock To: Alexander Mikhalitsyn Cc: Kees Cook , Andrew Morton , Cyrill Gorcunov , Mike Rapoport , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, criu@lists.linux.dev, Chen Ridong , Christian Brauner , David Hildenbrand , Eric Biederman , Lorenzo Stoakes , Michal Koutny Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: BC643160002 X-Rspamd-Server: rspam07 X-Stat-Signature: gj86mf6sncf967mpdx8ocwwuk4xrggp5 X-HE-Tag: 1770772138-128064 X-HE-Meta: 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 ansKCwLE kgto/Eubl+T81q/YYta5DZuFqs9a0IjyrSpvmNtv1KGzj7Aws4amLpycnPCuQhSY0whddLfOxTWNQl0YuDBWSIGw9ZW11e3VEvRQEr6PI7PUKiOjOCzZnfakwTEnVPHiDwJdlEuITZC+rtyCPsrEj7Ma6+HT6fMg24I663t7PCNo+YDdbDPNPOjgSk73Dklbl4t1rotDJXG1HNySZu8ixx/Md+HaXDpO+r6ZSwIu/UqycgZQYUDM+QAl160Ti06Q4VpPtFv2Rl/ze84Bz6zt/fVrwHQ6uUwp/7OwcOG7JhyjHxCv6GbUlmblhpPwfN7EX8l2tqb9nKzzMdW1zY4qFDuv5hsUmytTr6NcEi7ykPBXyGQje4C6LEm+IAg== 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 Tue, Feb 10, 2026 at 12:36=E2=80=AFPM Alexander Mikhalitsyn wrote: > .... > > static const struct file_operations proc_auxv_operations =3D { > > diff --git a/kernel/fork.c b/kernel/fork.c > > index 0091315643de..c0a3dd94df22 100644 > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -1104,8 +1104,13 @@ static struct mm_struct *mm_init(struct mm_struc= t *mm, struct task_struct *p, > > __mm_flags_overwrite_word(mm, mmf_init_legacy_flags(fla= gs)); > > mm->def_flags =3D current->mm->def_flags & VM_INIT_DEF_= MASK; > > > > - if (mm_flags_test(MMF_USER_HWCAP, current->mm)) > > + if (mm_flags_test(MMF_USER_HWCAP, current->mm)) { > > + spin_lock(¤t->mm->arg_lock); > > mm_flags_set(MMF_USER_HWCAP, mm); > > + memcpy(mm->saved_auxv, current->mm->saved_auxv, > > + sizeof(mm->saved_auxv)); > > nit: I was looking for this memcpy(mm->saved_auxv, > current->mm->saved_auxv, sizeof(mm->saved_auxv)) while reviewing > a previous patch. Shouldn't it be there? > No, it should not. dup_mm copies the contents of the old mm to the new one immediately after allocation, but it does so without holding any locks. Thanks, Andrei