From c5785fdf1d660eaefb9711284414262d0cfe8843 Mon Sep 17 00:00:00 2001 From: Adam Majer Date: Fri, 17 Aug 2018 14:48:17 +0800 Subject: [PATCH] Verify that we are not reading past end of a buffer Simple reproducer is just, ret &d:ep which triggers a buffer overread due to parsing of an invalid segment override. Signed-off-by: Adam Majer Upstream-Status: Submitted [https://bugzilla.nasm.us/show_bug.cgi?id=3392447] CVE: CVE-2018-8883 Signed-off-by: Hongxu Jia --- include/opflags.h | 2 +- include/tables.h | 1 + x86/regs.pl | 3 ++- 3 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/opflags.h b/include/opflags.h index ef2838c1..8d4b6b1e 100644 --- a/include/opflags.h +++ b/include/opflags.h @@ -166,7 +166,7 @@ #define REG_CLASS_BND GEN_REG_CLASS(9) #define is_class(class, op) (!((opflags_t)(class) & ~(opflags_t)(op))) -#define is_reg_class(class, reg) is_class((class), nasm_reg_flags[(reg)]) +#define is_reg_class(class, reg) is_class((class), ((reg) < nasm_reg_flags_size ? nasm_reg_flags[(reg)] : 0)) #define IS_SREG(reg) is_reg_class(REG_SREG, (reg)) #define IS_FSGS(reg) is_reg_class(REG_FSGS, (reg)) diff --git a/include/tables.h b/include/tables.h index 24a665e2..458752ce 100644 --- a/include/tables.h +++ b/include/tables.h @@ -64,6 +64,7 @@ extern const char * const nasm_reg_names[]; typedef uint64_t opflags_t; typedef uint16_t decoflags_t; extern const opflags_t nasm_reg_flags[]; +extern const size_t nasm_reg_flags_size; /* regvals.c */ extern const int nasm_regvals[]; diff --git a/x86/regs.pl b/x86/regs.pl index 3a1b56f5..cb5cea68 100755 --- a/x86/regs.pl +++ b/x86/regs.pl @@ -158,7 +158,8 @@ if ( $fmt eq 'h' ) { printf " %-15s /* %-5s */\n", $regs{$reg}.',', $reg; } - print "};\n"; + print "};\n\n"; + print "const size_t nasm_reg_flags_size = sizeof(nasm_reg_flags) / sizeof(opflags_t);\n"; } elsif ( $fmt eq 'vc' ) { # Output regvals.c print "/* automatically generated from $file - do not edit */\n\n"; -- 2.17.1