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J . Lu" , Yu-cheng Yu , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, libc-alpha@sourceware.org Subject: Re: [PATCH v1 1/2] elf: Allow architectures to parse properties on the main executable Message-ID: <20210603154018.GG4187@arm.com> References: <20210521144621.9306-1-broonie@kernel.org> <20210521144621.9306-2-broonie@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210521144621.9306-2-broonie@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210603_164128_340754_956AA2E3 X-CRM114-Status: GOOD ( 32.20 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, May 21, 2021 at 03:46:20PM +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 > --- > arch/arm64/include/asm/elf.h | 3 ++- > fs/binfmt_elf.c | 25 +++++++++++++++++-------- > include/linux/elf.h | 4 +++- > 3 files changed, 22 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h > index 8d1c8dcb87fd..c8678a8c36d5 100644 > --- a/arch/arm64/include/asm/elf.h > +++ b/arch/arm64/include/asm/elf.h > @@ -261,6 +261,7 @@ struct arch_elf_state { > > static inline int arch_parse_elf_property(u32 type, const void *data, > size_t datasz, bool compat, > + bool is_interp, > struct arch_elf_state *arch) > { > /* No known properties for AArch32 yet */ > @@ -273,7 +274,7 @@ static inline int arch_parse_elf_property(u32 type, const void *data, > if (datasz != sizeof(*p)) > return -ENOEXEC; > > - if (system_supports_bti() && > + if (system_supports_bti() && is_interp && Won't this cause BTI to be forced off for static binaries? Perhaps this should be (has_interp == is_interp), as for arch_elf_adjust_prot(). Seems gross though, since has_interp would become useless after the next patch. If there's no sensible way to keep this bisectable, perhaps the patches can be merged instead. (has_interp should probably also go away for arch_elf_adjust_prot() -- see my comments on the next patch). > (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) > arch->flags |= ARM64_ELF_BTI; > } > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 187b3f2b9202..c8397664af39 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -716,7 +716,7 @@ 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, > + struct arch_elf_state *arch, bool is_interp, > bool have_prev_type, u32 *prev_type) > { > size_t o, step; > @@ -751,7 +751,8 @@ 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, is_interp, > + arch); > if (ret) > return ret; > > @@ -764,7 +765,7 @@ 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, > - struct arch_elf_state *arch) > + bool is_interp, struct arch_elf_state *arch) > { > union { > struct elf_note nhdr; > @@ -813,7 +814,8 @@ 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); > + is_interp, have_prev_type, > + &prev_type); > have_prev_type = true; > } while (!ret); > > @@ -828,6 +830,7 @@ 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 +966,11 @@ 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; (Hmm, this actually looks a bit cleaner than just clobbering elf_property_phdata with the interpreter properties as was done previously.) > break; > > case PT_LOPROC ... PT_HIPROC: > @@ -979,10 +981,17 @@ static int load_elf_binary(struct linux_binprm *bprm) > goto out_free_dentry; > break; > } > + > + retval = parse_elf_properties(interpreter, > + interp_elf_property_phdata, > + true, &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, > + false, &arch_state); > if (retval) > goto out_free_dentry; > > diff --git a/include/linux/elf.h b/include/linux/elf.h > index c9a46c4e183b..a20dcdcd86c5 100644 > --- a/include/linux/elf.h > +++ b/include/linux/elf.h > @@ -88,13 +88,15 @@ struct arch_elf_state; > #ifndef CONFIG_ARCH_USE_GNU_PROPERTY > static inline int arch_parse_elf_property(u32 type, const void *data, > size_t datasz, bool compat, > + bool is_interp, > struct arch_elf_state *arch) > { > return 0; > } > #else > extern int arch_parse_elf_property(u32 type, const void *data, size_t datasz, > - bool compat, struct arch_elf_state *arch); > + bool compat, bool is_interp, > + struct arch_elf_state *arch); > #endif Looks like a sensible change, modulo my comments above. You may want to Cc Yu-cheng Yu when reposting, since this would affect his patches (trivially though). Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel