From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by sourceware.org (Postfix) with ESMTP id 2010E3848025 for ; Wed, 9 Jun 2021 15:17:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 2010E3848025 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C9DF0D6E; Wed, 9 Jun 2021 08:17:26 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 76C653F73D; Wed, 9 Jun 2021 08:17:25 -0700 (PDT) Date: Wed, 9 Jun 2021 16:16:25 +0100 From: Dave Martin To: Mark Brown Cc: Catalin Marinas , Will Deacon , Szabolcs Nagy , Jeremy Linton , "H . J . Lu" , Yu-cheng Yu , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, libc-alpha@sourceware.org Subject: Re: [PATCH v2 1/3] elf: Allow architectures to parse properties on the main executable Message-ID: <20210609151622.GK4187@arm.com> References: <20210604112450.13344-1-broonie@kernel.org> <20210604112450.13344-2-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210604112450.13344-2-broonie@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 Jun 2021 15:17:28 -0000 On Fri, Jun 04, 2021 at 12:24:48PM +0100, Mark Brown wrote: > Currently the ELF code only attempts to parse properties on the image > that will start execution, either the interpreter or for statically linked > executables the main executable. The expectation is that any property > handling for the main executable will be done by the interpreter. This is > a bit inconsistent since we do map the executable and is causing problems > for the arm64 BTI support when used in conjunction with systemd's use of > seccomp to implement MemoryDenyWriteExecute which stops the dynamic linker > adjusting the permissions of executable segments. > > Allow architectures to handle properties for both the dynamic linker and > main executable, adjusting arch_parse_elf_properties() to have an is_interp > flag as with arch_elf_adjust_prot() and calling it for both the main > executable and any intepreter. > > Signed-off-by: Mark Brown I haven't got my head around whether we must move some of the arm64 logic from arch_elf_adjust_proc() to arch_parse_elf_properties(), but either way, it would make sense to explain the direction of travel here. (This may just be me failing to keep track of what's changing -- the affected logic is retained for bisectability here and then dropped later on in the series...) It's a little annoying that we add has_interp all over the place only to remove it again later, but I guess that may be the simplest way to keep things bisectable while moving logic around. If so, I don't have a strong opinion on it. [...] > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 187b3f2b9202..253ca9969345 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -716,8 +716,9 @@ static unsigned long load_elf_interp(struct elfhdr *interp_elf_ex, > */ > > static int parse_elf_property(const char *data, size_t *off, size_t datasz, > - struct arch_elf_state *arch, > - bool have_prev_type, u32 *prev_type) > + struct arch_elf_state *arch, bool has_interp, > + bool is_interp, bool have_prev_type, > + u32 *prev_type) > { > size_t o, step; > const struct gnu_property *pr; > @@ -751,7 +752,8 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, > *prev_type = pr->pr_type; > > ret = arch_parse_elf_property(pr->pr_type, data + o, > - pr->pr_datasz, ELF_COMPAT, arch); > + pr->pr_datasz, ELF_COMPAT, > + has_interp, is_interp, arch); > if (ret) > return ret; > > @@ -764,6 +766,7 @@ static int parse_elf_property(const char *data, size_t *off, size_t datasz, > #define NOTE_NAME_SZ (sizeof(GNU_PROPERTY_TYPE_0_NAME)) > > static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, > + bool has_interp, bool is_interp, > struct arch_elf_state *arch) > { > union { > @@ -813,7 +816,8 @@ static int parse_elf_properties(struct file *f, const struct elf_phdr *phdr, > have_prev_type = false; > do { > ret = parse_elf_property(note.data, &off, datasz, arch, > - have_prev_type, &prev_type); > + has_interp, is_interp, have_prev_type, > + &prev_type); > have_prev_type = true; > } while (!ret); > > @@ -828,6 +832,7 @@ static int load_elf_binary(struct linux_binprm *bprm) > unsigned long error; > struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata = NULL; > struct elf_phdr *elf_property_phdata = NULL; > + struct elf_phdr *interp_elf_property_phdata = NULL; > unsigned long elf_bss, elf_brk; > int bss_prot = 0; > int retval, i; > @@ -963,12 +968,11 @@ static int load_elf_binary(struct linux_binprm *bprm) > goto out_free_dentry; > > /* Pass PT_LOPROC..PT_HIPROC headers to arch code */ > - elf_property_phdata = NULL; > elf_ppnt = interp_elf_phdata; > for (i = 0; i < interp_elf_ex->e_phnum; i++, elf_ppnt++) > switch (elf_ppnt->p_type) { > case PT_GNU_PROPERTY: > - elf_property_phdata = elf_ppnt; > + interp_elf_property_phdata = elf_ppnt; > break; > > case PT_LOPROC ... PT_HIPROC: > @@ -979,10 +983,17 @@ static int load_elf_binary(struct linux_binprm *bprm) > goto out_free_dentry; > break; > } > + > + retval = parse_elf_properties(interpreter, > + interp_elf_property_phdata, > + true, true, &arch_state); > + if (retval) > + goto out_free_dentry; > + > } > > - retval = parse_elf_properties(interpreter ?: bprm->file, > - elf_property_phdata, &arch_state); > + retval = parse_elf_properties(bprm->file, elf_property_phdata, > + interpreter, false, &arch_state); Nit: interpreter != NULL? (I guess it works as-is, but from the way this is written it looks a little like we intend parse_elf_properties() to examine / modify *interpreter, which is not the case. > if (retval) > goto out_free_dentry; > [...] Cheers ---Dave