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Wed, 04 Dec 2024 10:15:33 -0800 (PST) MIME-Version: 1.0 References: <20240806214931.2198172-1-jeffxu@google.com> <20240806214931.2198172-2-jeffxu@google.com> <20241204190429.0a18dd22@mordecai.tesarici.cz> In-Reply-To: <20241204190429.0a18dd22@mordecai.tesarici.cz> From: Jeff Xu Date: Wed, 4 Dec 2024 10:15:21 -0800 Message-ID: Subject: Re: [PATCH v2 1/1] binfmt_elf: mseal address zero To: =?UTF-8?B?UGV0ciBUZXNhxZnDrWs=?= Cc: akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com, sroettger@google.com, adhemerval.zanella@linaro.org, ojeda@kernel.org, adobriyan@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jorgelo@chromium.org, linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 6925320019 X-Stat-Signature: 5adxdux9ydqrsfrmeomob6xkibdbhoqk X-Rspam-User: X-HE-Tag: 1733336118-184314 X-HE-Meta: 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 RsjrWkuS vmf7CifQVRyJ04z+/5SiTC8EF3tZadNMLmi6qOQNCD7XKrUfh/dZtHvCcsw35K2c2jYaDbXTCW8mYMQwhQg4h/edKkFKAfb4ks8JM4KPhoR9J4g/vHSDd4Mw6eGjAUHPIdXN6L6HqawA7isV5DiifAcV+gaiqAhY8VtH8eimSAV7YI8kNZpQWI9bcS7wzGr7uFLqfBk8R4nw0Vv+8jbaxyudJrJyIsjg3tLwqySUzPklkRuMTO3Wz4Z86KOb050ilcxSCm2bupGU/lYI= 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, Dec 4, 2024 at 10:04=E2=80=AFAM Petr Tesa=C5=99=C3=ADk wrote: > > On Tue, 6 Aug 2024 21:49:27 +0000 > jeffxu@chromium.org wrote: > > > From: Jeff Xu > > > > Some legacy SVr4 apps might depend on page on address zero > > to be readable, however I can't find a reason that the page > > ever becomes writeable, so seal it. > > > > If there is a compain, we can make this configurable. > > > > Signed-off-by: Jeff Xu > > --- > > fs/binfmt_elf.c | 5 +++++ > > include/linux/mm.h | 10 ++++++++++ > > mm/mseal.c | 2 +- > > 3 files changed, 16 insertions(+), 1 deletion(-) > > > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > > index 19fa49cd9907..f839fa228509 100644 > > --- a/fs/binfmt_elf.c > > +++ b/fs/binfmt_elf.c > > @@ -1314,6 +1314,11 @@ static int load_elf_binary(struct linux_binprm *= bprm) > > emulate the SVr4 behavior. Sigh. */ > > error =3D vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EX= EC, > > MAP_FIXED | MAP_PRIVATE, 0); > > + > > + retval =3D do_mseal(0, PAGE_SIZE, 0); > > + if (retval) > > + pr_warn("pid=3D%d, couldn't seal address 0, ret= =3D%d.\n", > > + task_pid_nr(current), retval); > > } > > > > regs =3D current_pt_regs(); > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index c4b238a20b76..a178c15812eb 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -4201,4 +4201,14 @@ void vma_pgtable_walk_end(struct vm_area_struct = *vma); > > > > int reserve_mem_find_by_name(const char *name, phys_addr_t *start, phy= s_addr_t *size); > > > > +#ifdef CONFIG_64BIT > > Strictly speaking, this should be > > #if defined(CONFIG_64BIT) && defined(CONFIG_MMU) > > But since we do not support any 64-bit architecture without MMU, I'm > just making this marginal note, so it can be found in ML archives if > needed. > Noted. Thanks! > Petr T