From 1b09e67353f46f2ff9039da78a37d7717155df08 Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Thu, 17 Mar 2022 13:58:56 +0100 Subject: [PATCH] libelf: Take map offset into account for Shdr alignment check in elf_begin The sh_num function tries to get at the zero section Shdr directly. When the file is mmapped it has to make sure the offset into the file to the start of the Elf structure is taken into account when trying to cast the address to make sure the alignment is correct. Signed-off-by: Mark Wielaard --- libelf/ChangeLog | 5 +++++ libelf/elf_begin.c | 8 +++++--- 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/libelf/ChangeLog b/libelf/ChangeLog index 29a8aae..1883af0 100644 --- a/libelf/ChangeLog +++ b/libelf/ChangeLog @@ -1,3 +1,8 @@ +2022-03-17 Mark Wielaard + + * elf_begin.c (get_shnum): Take offset into account for Shdr + alignment check. + 2021-12-19 Mark Wielaard * elf_begin.c (file_read_elf): Cast ehdr to uintptr_t before e_shoff diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c index 0c9a988..53bbff4 100644 --- a/libelf/elf_begin.c +++ b/libelf/elf_begin.c @@ -1,6 +1,6 @@ /* Create descriptor for processing file. Copyright (C) 1998-2010, 2012, 2014, 2015, 2016 Red Hat, Inc. - Copyright (C) 2021 Mark J. Wielaard + Copyright (C) 2021, 2022 Mark J. Wielaard This file is part of elfutils. Written by Ulrich Drepper , 1998. @@ -158,7 +158,8 @@ get_shnum (void *map_address, unsigned char *e_ident, int fildes, if (likely (map_address != NULL) && e_ident[EI_DATA] == MY_ELFDATA && (ALLOW_UNALIGNED - || (((size_t) ((char *) map_address + ehdr.e32->e_shoff)) + || (((size_t) ((char *) (map_address + ehdr.e32->e_shoff + + offset))) & (__alignof__ (Elf32_Shdr) - 1)) == 0)) /* We can directly access the memory. */ result = ((Elf32_Shdr *) ((char *) map_address + ehdr.e32->e_shoff @@ -218,7 +219,8 @@ get_shnum (void *map_address, unsigned char *e_ident, int fildes, Elf64_Xword size; if (likely (map_address != NULL) && e_ident[EI_DATA] == MY_ELFDATA && (ALLOW_UNALIGNED - || (((size_t) ((char *) map_address + ehdr.e64->e_shoff)) + || (((size_t) ((char *) (map_address + ehdr.e64->e_shoff + + offset))) & (__alignof__ (Elf64_Shdr) - 1)) == 0)) /* We can directly access the memory. */ size = ((Elf64_Shdr *) ((char *) map_address + ehdr.e64->e_shoff -- 2.7.4