From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0777C433FE for ; Thu, 17 Nov 2022 22:07:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241127AbiKQWHa (ORCPT ); Thu, 17 Nov 2022 17:07:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241372AbiKQWHM (ORCPT ); Thu, 17 Nov 2022 17:07:12 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91F4274CFE; Thu, 17 Nov 2022 14:06:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id BC905CE1F67; Thu, 17 Nov 2022 22:06:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEC34C433B5; Thu, 17 Nov 2022 22:06:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668722807; bh=xsaepc7zrHeiaxqJ99aKuvc3jgRcvS86nP1WzqMV8jw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=MdsvT1wVx/V5LmEKxToxtewAEZMIayQD7XJ72/P88rlAN0JRlphUNueuyF5WdD54b MYTC44+zeU52n9KJxt02qDNYabHN0dpJivv4966Pt972spVc0G6WcN4+y5kFq+ujnN 5a2ULPI/W1MFQyXZtonR5Z0L/jdBfq9XABeczticsItPXKW6RUgELrYjnbualsA0KK rtOKg8sPsGsZ6Hq0d4teJWNUrFk4g+q8oqOCqSwyw8Qr8coi/b1mH9WvDiOqZydzhE iba0PM+gH9D6OJdeoBkm4bJfhZeAmYlEhHlTgZOJwcrFpKHlkfRd6g9Fx5qFe/n0Ko 0FTdsvUWfQeFw== Received: by mail-ej1-f51.google.com with SMTP id f18so8604102ejz.5; Thu, 17 Nov 2022 14:06:47 -0800 (PST) X-Gm-Message-State: ANoB5pkDBOBKrIkvauJ3CfdpRfApCYb5Xy6BAgmS9zllPfyNJQ/anIWf Sem58DlSnvkRQkAhdbWLgBPoet4/VEWuWA4CY0M= X-Google-Smtp-Source: AA0mqf5BOFW1Wno15LQFILchmFZf33Kcq3irHyykuYmt1xPuWgPSCzg+NKiM61LVhFymFp1IGCke7SkHtPN9nXnBHUc= X-Received: by 2002:a17:906:2645:b0:781:d0c1:4434 with SMTP id i5-20020a170906264500b00781d0c14434mr3693058ejc.756.1668722804839; Thu, 17 Nov 2022 14:06:44 -0800 (PST) MIME-Version: 1.0 References: <20220901171252.2148348-1-song@kernel.org> In-Reply-To: <20220901171252.2148348-1-song@kernel.org> From: Song Liu Date: Thu, 17 Nov 2022 14:06:32 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6] livepatch: Clear relocation targets on a module removal To: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Cc: jpoimboe@kernel.org, jikos@kernel.org, mbenes@suse.cz, pmladek@suse.com, x86@kernel.org, joe.lawrence@redhat.com, linuxppc-dev@lists.ozlabs.org, Josh Poimboeuf Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi folks, It seems we forgot about this work... What shall we do to move forward? Thanks, Song On Thu, Sep 1, 2022 at 10:16 AM Song Liu wrote: > > From: Miroslav Benes > > Josh reported a bug: > > When the object to be patched is a module, and that module is > rmmod'ed and reloaded, it fails to load with: > > module: x86/modules: Skipping invalid relocation target, existing value is nonzero for type 2, loc 00000000ba0302e9, val ffffffffa03e293c > livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8) > livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd' > > The livepatch module has a relocation which references a symbol > in the _previous_ loading of nfsd. When apply_relocate_add() > tries to replace the old relocation with a new one, it sees that > the previous one is nonzero and it errors out. > > On ppc64le, we have a similar issue: > > module_64: livepatch_nfsd: Expected nop after call, got e8410018 at e_show+0x60/0x548 [livepatch_nfsd] > livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8) > livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd' > > He also proposed three different solutions. We could remove the error > check in apply_relocate_add() introduced by commit eda9cec4c9a1 > ("x86/module: Detect and skip invalid relocations"). However the check > is useful for detecting corrupted modules. > > We could also deny the patched modules to be removed. If it proved to be > a major drawback for users, we could still implement a different > approach. The solution would also complicate the existing code a lot. > > We thus decided to reverse the relocation patching (clear all relocation > targets on x86_64). The solution is not > universal and is too much arch-specific, but it may prove to be simpler > in the end. > > Reported-by: Josh Poimboeuf > Signed-off-by: Miroslav Benes > Signed-off-by: Song Liu > > --- > > NOTE: powerpc32 code is only compile tested. > > Changes v5 = v6: > 1. Fix powerpc64. > 2. Fix compile for powerpc32. > > Changes v4 = v5: > 1. Fix compile with powerpc. > > Changes v3 = v4: > 1. Reuse __apply_relocate_add to make it more reliable in long term. > (Josh Poimboeuf) > 2. Add back ppc64 logic from v2, with changes to match current code. > (Josh Poimboeuf) > > Changes v2 => v3: > 1. Rewrite x86 changes to match current code style. > 2. Remove powerpc changes as there is no test coverage in v3. > 3. Only keep 1/3 of v2. > > v2: https://lore.kernel.org/all/20190905124514.8944-1-mbenes@suse.cz/T/#u > --- > arch/powerpc/kernel/module_32.c | 10 ++++ > arch/powerpc/kernel/module_64.c | 49 +++++++++++++++ > arch/s390/kernel/module.c | 8 +++ > arch/x86/kernel/module.c | 102 +++++++++++++++++++++++--------- > include/linux/moduleloader.h | 7 +++ > kernel/livepatch/core.c | 41 ++++++++++++- > 6 files changed, 189 insertions(+), 28 deletions(-) > > diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c > index ea6536171778..e3c312770453 100644 > --- a/arch/powerpc/kernel/module_32.c > +++ b/arch/powerpc/kernel/module_32.c > @@ -285,6 +285,16 @@ int apply_relocate_add(Elf32_Shdr *sechdrs, > return 0; > } > > +#ifdef CONFIG_LIVEPATCH > +void clear_relocate_add(Elf32_Shdr *sechdrs, > + const char *strtab, > + unsigned int symindex, > + unsigned int relsec, > + struct module *me) > +{ > +} > +#endif > + > #ifdef CONFIG_DYNAMIC_FTRACE > notrace int module_trampoline_target(struct module *mod, unsigned long addr, > unsigned long *target) > diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c > index 7e45dc98df8a..514951f97391 100644 > --- a/arch/powerpc/kernel/module_64.c > +++ b/arch/powerpc/kernel/module_64.c > @@ -739,6 +739,55 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > return 0; > } > > +#ifdef CONFIG_LIVEPATCH > +void clear_relocate_add(Elf64_Shdr *sechdrs, > + const char *strtab, > + unsigned int symindex, > + unsigned int relsec, > + struct module *me) > +{ > + unsigned int i; > + Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr; > + Elf64_Sym *sym; > + unsigned long *location; > + const char *symname; > + u32 *instruction; > + > + pr_debug("Clearing ADD relocate section %u to %u\n", relsec, > + sechdrs[relsec].sh_info); > + > + for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { > + location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr > + + rela[i].r_offset; > + sym = (Elf64_Sym *)sechdrs[symindex].sh_addr > + + ELF64_R_SYM(rela[i].r_info); > + symname = me->core_kallsyms.strtab > + + sym->st_name; > + > + if (ELF64_R_TYPE(rela[i].r_info) != R_PPC_REL24) > + continue; > + /* > + * reverse the operations in apply_relocate_add() for case > + * R_PPC_REL24. > + */ > + if (sym->st_shndx != SHN_UNDEF && > + sym->st_shndx != SHN_LIVEPATCH) > + continue; > + > + instruction = (u32 *)location; > + if (is_mprofile_ftrace_call(symname)) > + continue; > + > + if (!instr_is_relative_link_branch(ppc_inst(*instruction))) > + continue; > + > + instruction += 1; > + patch_instruction(instruction, ppc_inst(PPC_RAW_NOP())); > + } > + > +} > +#endif > + > #ifdef CONFIG_DYNAMIC_FTRACE > int module_trampoline_target(struct module *mod, unsigned long addr, > unsigned long *target) > diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c > index 2d159b32885b..cc6784fbc1ac 100644 > --- a/arch/s390/kernel/module.c > +++ b/arch/s390/kernel/module.c > @@ -500,6 +500,14 @@ static int module_alloc_ftrace_hotpatch_trampolines(struct module *me, > } > #endif /* CONFIG_FUNCTION_TRACER */ > > +#ifdef CONFIG_LIVEPATCH > +void clear_relocate_add(Elf64_Shdr *sechdrs, const char *strtab, > + unsigned int symindex, unsigned int relsec, > + struct module *me) > +{ > +} > +#endif > + > int module_finalize(const Elf_Ehdr *hdr, > const Elf_Shdr *sechdrs, > struct module *me) > diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c > index b1abf663417c..f9632afbb84c 100644 > --- a/arch/x86/kernel/module.c > +++ b/arch/x86/kernel/module.c > @@ -128,18 +128,20 @@ int apply_relocate(Elf32_Shdr *sechdrs, > return 0; > } > #else /*X86_64*/ > -static int __apply_relocate_add(Elf64_Shdr *sechdrs, > +static int __apply_clear_relocate_add(Elf64_Shdr *sechdrs, > const char *strtab, > unsigned int symindex, > unsigned int relsec, > struct module *me, > - void *(*write)(void *dest, const void *src, size_t len)) > + void *(*write)(void *dest, const void *src, size_t len), > + bool clear) > { > unsigned int i; > Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; > Elf64_Sym *sym; > void *loc; > u64 val; > + u64 zero = 0ULL; > > DEBUGP("Applying relocate section %u to %u\n", > relsec, sechdrs[relsec].sh_info); > @@ -163,40 +165,60 @@ static int __apply_relocate_add(Elf64_Shdr *sechdrs, > case R_X86_64_NONE: > break; > case R_X86_64_64: > - if (*(u64 *)loc != 0) > - goto invalid_relocation; > - write(loc, &val, 8); > + if (!clear) { > + if (*(u64 *)loc != 0) > + goto invalid_relocation; > + write(loc, &val, 8); > + } else { > + write(loc, &zero, 8); > + } > break; > case R_X86_64_32: > - if (*(u32 *)loc != 0) > - goto invalid_relocation; > - write(loc, &val, 4); > - if (val != *(u32 *)loc) > - goto overflow; > + if (!clear) { > + if (*(u32 *)loc != 0) > + goto invalid_relocation; > + write(loc, &val, 4); > + if (val != *(u32 *)loc) > + goto overflow; > + } else { > + write(loc, &zero, 4); > + } > break; > case R_X86_64_32S: > - if (*(s32 *)loc != 0) > - goto invalid_relocation; > - write(loc, &val, 4); > - if ((s64)val != *(s32 *)loc) > - goto overflow; > + if (!clear) { > + if (*(s32 *)loc != 0) > + goto invalid_relocation; > + write(loc, &val, 4); > + if ((s64)val != *(s32 *)loc) > + goto overflow; > + } else { > + write(loc, &zero, 4); > + } > break; > case R_X86_64_PC32: > case R_X86_64_PLT32: > - if (*(u32 *)loc != 0) > - goto invalid_relocation; > - val -= (u64)loc; > - write(loc, &val, 4); > + if (!clear) { > + if (*(u32 *)loc != 0) > + goto invalid_relocation; > + val -= (u64)loc; > + write(loc, &val, 4); > #if 0 > - if ((s64)val != *(s32 *)loc) > - goto overflow; > + if ((s64)val != *(s32 *)loc) > + goto overflow; > #endif > + } else { > + write(loc, &zero, 4); > + } > break; > case R_X86_64_PC64: > - if (*(u64 *)loc != 0) > - goto invalid_relocation; > - val -= (u64)loc; > - write(loc, &val, 8); > + if (!clear) { > + if (*(u64 *)loc != 0) > + goto invalid_relocation; > + val -= (u64)loc; > + write(loc, &val, 8); > + } else { > + write(loc, &zero, 8); > + } > break; > default: > pr_err("%s: Unknown rela relocation: %llu\n", > @@ -234,8 +256,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > mutex_lock(&text_mutex); > } > > - ret = __apply_relocate_add(sechdrs, strtab, symindex, relsec, me, > - write); > + ret = __apply_clear_relocate_add(sechdrs, strtab, symindex, relsec, me, > + write, false /* clear */); > > if (!early) { > text_poke_sync(); > @@ -245,6 +267,32 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, > return ret; > } > > +#ifdef CONFIG_LIVEPATCH > + > +void clear_relocate_add(Elf64_Shdr *sechdrs, > + const char *strtab, > + unsigned int symindex, > + unsigned int relsec, > + struct module *me) > +{ > + bool early = me->state == MODULE_STATE_UNFORMED; > + void *(*write)(void *, const void *, size_t) = memcpy; > + > + if (!early) { > + write = text_poke; > + mutex_lock(&text_mutex); > + } > + > + __apply_clear_relocate_add(sechdrs, strtab, symindex, relsec, me, > + write, true /* clear */); > + > + if (!early) { > + text_poke_sync(); > + mutex_unlock(&text_mutex); > + } > +} > +#endif > + > #endif > > int module_finalize(const Elf_Ehdr *hdr, > diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h > index 9e09d11ffe5b..958e6da7f475 100644 > --- a/include/linux/moduleloader.h > +++ b/include/linux/moduleloader.h > @@ -72,6 +72,13 @@ int apply_relocate_add(Elf_Shdr *sechdrs, > unsigned int symindex, > unsigned int relsec, > struct module *mod); > +#ifdef CONFIG_LIVEPATCH > +void clear_relocate_add(Elf_Shdr *sechdrs, > + const char *strtab, > + unsigned int symindex, > + unsigned int relsec, > + struct module *me); > +#endif > #else > static inline int apply_relocate_add(Elf_Shdr *sechdrs, > const char *strtab, > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > index bc475e62279d..5c0d8a4eba13 100644 > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -316,6 +316,45 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, > return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); > } > > +static void klp_clear_object_relocations(struct module *pmod, > + struct klp_object *obj) > +{ > + int i, cnt; > + const char *objname, *secname; > + char sec_objname[MODULE_NAME_LEN]; > + Elf_Shdr *sec; > + > + objname = klp_is_module(obj) ? obj->name : "vmlinux"; > + > + /* For each klp relocation section */ > + for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) { > + sec = pmod->klp_info->sechdrs + i; > + secname = pmod->klp_info->secstrings + sec->sh_name; > + if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) > + continue; > + > + /* > + * Format: .klp.rela.sec_objname.section_name > + * See comment in klp_resolve_symbols() for an explanation > + * of the selected field width value. > + */ > + secname = pmod->klp_info->secstrings + sec->sh_name; > + cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname); > + if (cnt != 1) { > + pr_err("section %s has an incorrectly formatted name\n", > + secname); > + continue; > + } > + > + if (strcmp(objname, sec_objname)) > + continue; > + > + clear_relocate_add(pmod->klp_info->sechdrs, > + pmod->core_kallsyms.strtab, > + pmod->klp_info->symndx, i, pmod); > + } > +} > + > /* > * Sysfs Interface > * > @@ -1154,7 +1193,7 @@ static void klp_cleanup_module_patches_limited(struct module *mod, > klp_unpatch_object(obj); > > klp_post_unpatch_callback(obj); > - > + klp_clear_object_relocations(patch->mod, obj); > klp_free_object_loaded(obj); > break; > } > -- > 2.30.2 >