From 9058abdd180843473d440958c79a1a781be723c1 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Tue, 27 Jul 2010 10:25:34 -0700 Subject: [PATCH] linux-user: Improve consistency checking in elf headers. Validate more fields of the elf header. Extract those checks into two common functions to be used in both load_elf_interp and load_elf_binary. Signed-off-by: Richard Henderson Signed-off-by: Edgar E. Iglesias --- linux-user/elfload.c | 57 +++++++++++++++++++++++++------------------- 1 file changed, 33 insertions(+), 24 deletions(-) diff --git a/linux-user/elfload.c b/linux-user/elfload.c index 6b57a91a3e..86872b27df 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -919,6 +919,30 @@ static int elf_core_dump(int, const CPUState *); #endif /* USE_ELF_CORE_DUMP */ static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias); +/* Verify the portions of EHDR within E_IDENT for the target. + This can be performed before bswapping the entire header. */ +static bool elf_check_ident(struct elfhdr *ehdr) +{ + return (ehdr->e_ident[EI_MAG0] == ELFMAG0 + && ehdr->e_ident[EI_MAG1] == ELFMAG1 + && ehdr->e_ident[EI_MAG2] == ELFMAG2 + && ehdr->e_ident[EI_MAG3] == ELFMAG3 + && ehdr->e_ident[EI_CLASS] == ELF_CLASS + && ehdr->e_ident[EI_DATA] == ELF_DATA + && ehdr->e_ident[EI_VERSION] == EV_CURRENT); +} + +/* Verify the portions of EHDR outside of E_IDENT for the target. + This has to wait until after bswapping the header. */ +static bool elf_check_ehdr(struct elfhdr *ehdr) +{ + return (elf_check_arch(ehdr->e_machine) + && ehdr->e_ehsize == sizeof(struct elfhdr) + && ehdr->e_phentsize == sizeof(struct elf_phdr) + && ehdr->e_shentsize == sizeof(struct elf_shdr) + && (ehdr->e_type == ET_EXEC || ehdr->e_type == ET_DYN)); +} + /* * 'copy_elf_strings()' copies argument/envelope strings from user * memory to free pages in kernel mem. These are in a format ready @@ -1150,33 +1174,16 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex, int i; bswap_ehdr(interp_elf_ex); - /* First of all, some simple consistency checks */ - if ((interp_elf_ex->e_type != ET_EXEC && - interp_elf_ex->e_type != ET_DYN) || - !elf_check_arch(interp_elf_ex->e_machine)) { + if (!elf_check_ehdr(interp_elf_ex)) { return ~((abi_ulong)0UL); } /* Now read in all of the header information */ - - if (sizeof(struct elf_phdr) * interp_elf_ex->e_phnum > TARGET_PAGE_SIZE) - return ~(abi_ulong)0UL; - elf_phdata = (struct elf_phdr *) malloc(sizeof(struct elf_phdr) * interp_elf_ex->e_phnum); - if (!elf_phdata) return ~((abi_ulong)0UL); - /* - * If the size of this structure has changed, then punt, since - * we will be doing the wrong thing. - */ - if (interp_elf_ex->e_phentsize != sizeof(struct elf_phdr)) { - free(elf_phdata); - return ~((abi_ulong)0UL); - } - i = interp_elf_ex->e_phnum * sizeof(struct elf_phdr); if (interp_elf_ex->e_phoff + i <= BPRM_BUF_SIZE) { memcpy(elf_phdata, bprm_buf + interp_elf_ex->e_phoff, i); @@ -1428,11 +1435,13 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs, load_addr = 0; load_bias = 0; elf_ex = *((struct elfhdr *) bprm->buf); /* exec-header */ - bswap_ehdr(&elf_ex); /* First of all, some simple consistency checks */ - if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) || - (! elf_check_arch(elf_ex.e_machine))) { + if (!elf_check_ident(&elf_ex)) { + return -ENOEXEC; + } + bswap_ehdr(&elf_ex); + if (!elf_check_ehdr(&elf_ex)) { return -ENOEXEC; } @@ -1444,7 +1453,8 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs, } /* Now read in all of the header information */ - elf_phdata = (struct elf_phdr *)malloc(elf_ex.e_phentsize*elf_ex.e_phnum); + elf_phdata = (struct elf_phdr *) + malloc(elf_ex.e_phnum * sizeof(struct elf_phdr)); if (elf_phdata == NULL) { return -ENOMEM; } @@ -1549,8 +1559,7 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs, interpreter_type = INTERPRETER_ELF; } - if (interp_elf_ex.e_ident[0] != 0x7f || - strncmp((char *)&interp_elf_ex.e_ident[1], "ELF",3) != 0) { + if (!elf_check_ident(&interp_elf_ex)) { interpreter_type &= ~INTERPRETER_ELF; }