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Tue, 8 Aug 2023 10:44:54 +0100 (BST) References: <20230807163705.9848-1-richard.henderson@linaro.org> <20230807163705.9848-5-richard.henderson@linaro.org> User-agent: mu4e 1.11.13; emacs 29.1.50 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Richard Henderson Cc: pbonzini@redhat.com, philmd@linaro.org, laurent@vivier.eu, deller@gmx.de, Akihiko Odaki , qemu-devel@nongnu.org Subject: Re: [PATCH for-8.1 v10 04/14] linux-user: Use MAP_FIXED_NOREPLACE for initial image mmap Date: Tue, 08 Aug 2023 10:43:09 +0100 In-reply-to: <20230807163705.9848-5-richard.henderson@linaro.org> Message-ID: <87o7jh98bt.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::435; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x435.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Richard Henderson writes: > Use this as extra protection for the guest mapping over > any qemu host mappings. > > Tested-by: Helge Deller > Reviewed-by: Helge Deller > Reviewed-by: Akihiko Odaki > Signed-off-by: Richard Henderson > --- > linux-user/elfload.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/linux-user/elfload.c b/linux-user/elfload.c > index 36e4026f05..1b4bb2d5af 100644 > --- a/linux-user/elfload.c > +++ b/linux-user/elfload.c > @@ -3147,8 +3147,11 @@ static void load_elf_image(const char *image_name,= int image_fd, > /* > * Reserve address space for all of this. > * > - * In the case of ET_EXEC, we supply MAP_FIXED so that we get > - * exactly the address range that is required. > + * In the case of ET_EXEC, we supply MAP_FIXED_NOREPLACE so that we = get > + * exactly the address range that is required. Without reserved_va, > + * the guest address space is not isolated. We have attempted to av= oid > + * conflict with the host program itself via probe_guest_base, but u= sing > + * MAP_FIXED_NOREPLACE instead of MAP_FIXED provides an extra check. > * > * Otherwise this is ET_DYN, and we are searching for a location > * that can hold the memory space required. If the image is > @@ -3160,7 +3163,7 @@ static void load_elf_image(const char *image_name, = int image_fd, > */ > load_addr =3D target_mmap(loaddr, (size_t)hiaddr - loaddr + 1, PROT_= NONE, > MAP_PRIVATE | MAP_ANON | MAP_NORESERVE | > - (ehdr->e_type =3D=3D ET_EXEC ? MAP_FIXED : 0= ), > + (ehdr->e_type =3D=3D ET_EXEC ? MAP_FIXED_NOR= EPLACE : 0), > -1, 0); We should probably also check the result =3D=3D load_addr for the places where MAP_FIXED_NOREPLACE isn't supported as we have this in osdep.h: #ifndef MAP_FIXED_NOREPLACE #define MAP_FIXED_NOREPLACE 0 #endif See 2667e069e7 (linux-user: don't use MAP_FIXED in pgd_find_hole_fallback) > if (load_addr =3D=3D -1) { > goto exit_mmap; --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro