From patchwork Sat Jul 28 04:49:53 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "H.J. Lu" X-Patchwork-Id: 28667 Received: (qmail 25886 invoked by alias); 28 Jul 2018 04:49:58 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 25876 invoked by uid 89); 28 Jul 2018 04:49:58 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-25.4 required=5.0 tests=AWL, BAYES_00, FREEMAIL_FROM, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy=crazy, yo X-HELO: mail-oi0-f65.google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to:cc; bh=HjGhq9D6T+VoSjrNPL15M/+r6uNczhiJQqJNqlyoWFY=; b=LY9jo/bY7oWfVn1SHcujhtCeYqnXOTUdp8UpKfyDpDKmZyNZ0gZwHnHgHREXbIuvDi KFJn4qI3XMWkhvqNdS+5Xt+rESnVRomkfneiJP45AAEoUEORMicA1JjSzkzgGM5CWCTG OiTQrjH/aWax9SVuTMg3+RjbksrqnRNzcT1ou6030QYGt40Qz4oL42uOBSxcdR8kioZF iPQ0+lF6j0UE7yr4mS/pgXiYKPh531T+2CyB6nBR7gCWYUieJG4XxUsFk6c7uaPNn+E9 ci2l/9QRtbSpxpVNAuLJ5xsyiiePo8dcf2bwkHfqwN1l4Uxa13fbeW/dlK3EfvBS2JOL aoKQ== MIME-Version: 1.0 From: "H.J. Lu" Date: Fri, 27 Jul 2018 21:49:53 -0700 Message-ID: Subject: [PATCH] x86/CET: Fix property note parser To: Florian Weimer Cc: GNU C Library , "Carlos O'Donell" On Fri, Jul 27, 2018 at 1:39 PM, Florian Weimer wrote: > On 07/27/2018 08:47 PM, H.J. Lu wrote: >> >> On Fri, Jul 27, 2018 at 11:26 AM, Florian Weimer >> wrote: >>> >>> On 07/27/2018 08:22 PM, H.J. Lu wrote: >>>> >>>> >>>> - while (1) >>>> + while (ptr < ptr_end) >>>> { >>>> unsigned int type = *(unsigned int *) ptr; >>>> unsigned int datasz = *(unsigned int *) (ptr + 4); >>> >>> >>> >>> You need 1 byte, but 8 bytes. Why is checking for at least 1 byte >>> sufficient here? >>> >> >> There is: >> >> /* Check for invalid property. */ >> if (note->n_descsz < 8 >> || (note->n_descsz % sizeof (ElfW(Addr))) != 0) >> break; >> >> before that. n_descsz should be correct. > > > I do not have a strong opinion regarding this matter. For correctly > generated notes, your patch should be fine. > There is a real bug in the note parser. It doesn't check each item. This test should fail on CET SDV since IBT is on and endbr64 is missing in foo. But it passed: [hjl@gnu-cet-1 bad-property-1]$ cat y.S #include .text .globl main .type main, @function main: .cfi_startproc endbr64 subq $8, %rsp .cfi_def_cfa_offset 16 movq $foo, %rdi call *%rdi xorl %eax, %eax addq $8, %rsp .cfi_def_cfa_offset 8 ret .cfi_endproc .size main, .-main .p2align 4,,15 .type foo, @function foo: .cfi_startproc ret .cfi_endproc .size foo, .-foo #if __SIZEOF_PTRDIFF_T__ == 8 # define ALIGN 3 #elif __SIZEOF_PTRDIFF_T__ == 4 # define ALIGN 2 #endif .section ".note.gnu.property", "a" .p2align ALIGN .long 1f - 0f /* name length */ .long 5f - 2f /* data length */ .long 5 /* note type */ 0: .asciz "GNU" /* vendor name */ 1: .p2align ALIGN 2: .long 1 /* pr_type. */ .long 4f - 3f /* pr_datasz. */ 3: .long 0x800 .long 0x800 4: .p2align ALIGN 5: .section .note.GNU-stack,"",@progbits [hjl@gnu-cet-1 bad-property-1]$ make y gcc -fcf-protection -c -o y.o y.S gcc -fcf-protection -g -o y y.o [hjl@gnu-cet-1 build-x86_64-linux]$ ../../glibc-cet-O3/build-x86_64-linux/elf/ld.so --library-path . ~/bugs/libc/bad-property-1/y [hjl@gnu-cet-1 build-x86_64-linux]$ This patch fixes it by properly checking each item and stops searching when a GNU_PROPERTY_X86_FEATURE_1_AND property is found regardless if its size is correct or not. Linker won't generate bad GNU_PROPERTY_X86_FEATURE_1_AND. But people may do crazy things. Starting program: /export/build/gnu/tools-build/glibc-cet/build-x86_64-linux/elf/ld.so --library-path . ~/bugs/libc/bad-property-1/y Program received signal SIGSEGV, Segmentation fault. 0x0000000000401130 in ?? () (gdb) disass 0x0000000000401130,+30 Dump of assembler code from 0x401130 to 0x40114e: => 0x0000000000401130: retq 0x0000000000401131: nopw %cs:0x0(%rax,%rax,1) 0x000000000040113b: nopl 0x0(%rax,%rax,1) 0x0000000000401140: endbr64 0x0000000000401144: push %r15 0x0000000000401146: mov %rdx,%r15 0x0000000000401149: push %r14 0x000000000040114b: mov %rsi,%r14 End of assembler dump. (gdb) OK for master? Thanks. From 75052a7f08a4261eb7c56885b56970ca96301d36 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Fri, 27 Jul 2018 20:34:55 -0700 Subject: [PATCH] x86/CET: Fix property note parser GNU_PROPERTY_X86_FEATURE_1_AND may not be the first property item. We need to properly check each property item until we reach the end of the property or find GNU_PROPERTY_X86_FEATURE_1_AND. * sysdeps/x86/dl-prop.h (_dl_process_cet_property_note): Parse each property item. --- sysdeps/x86/dl-prop.h | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/sysdeps/x86/dl-prop.h b/sysdeps/x86/dl-prop.h index 35d3f16a23..9e4d51a71d 100644 --- a/sysdeps/x86/dl-prop.h +++ b/sysdeps/x86/dl-prop.h @@ -73,7 +73,7 @@ _dl_process_cet_property_note (struct link_map *l, unsigned char *ptr = (unsigned char *) (note + 1) + 4; unsigned char *ptr_end = ptr + note->n_descsz; - while (ptr < ptr_end) + do { unsigned int type = *(unsigned int *) ptr; unsigned int datasz = *(unsigned int *) (ptr + 4); @@ -82,17 +82,23 @@ _dl_process_cet_property_note (struct link_map *l, if ((ptr + datasz) > ptr_end) break; - if (type == GNU_PROPERTY_X86_FEATURE_1_AND - && datasz == 4) + if (type == GNU_PROPERTY_X86_FEATURE_1_AND) { - unsigned int feature_1 = *(unsigned int *) ptr; - if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT)) - l->l_cet |= lc_ibt; - if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) - l->l_cet |= lc_shstk; + if (datasz == 4) + { + unsigned int feature_1 = *(unsigned int *) ptr; + if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_IBT)) + l->l_cet |= lc_ibt; + if ((feature_1 & GNU_PROPERTY_X86_FEATURE_1_SHSTK)) + l->l_cet |= lc_shstk; + } break; } + + /* Check the next property item. */ + ptr += ALIGN_UP (datasz, sizeof (ElfW(Addr))); } + while ((ptr_end - ptr) >= 8); } /* NB: Note sections like .note.ABI-tag and .note.gnu.build-id are -- 2.17.1