From 9bfe85ecddfd1a11376e7b4916f9b000aabd5da6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Timo=20Ter=C3=A4s?= Date: Tue, 1 Oct 2013 13:46:04 +0300 Subject: [PATCH] fs/binfmt_elf: fix memory map for PIE applications MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit arch/x86/include/asm/elf.h comment says: " ELF_ET_DYN_BASE is the location that an ET_DYN program is loaded if exec'ed. Typical use of this is to invoke "./ld.so someprog" to test out a new version of the loader. We need to make sure that it is out of the way of the program that it will "exec", and that there is sufficient room for the brk. " In case we have main application linked as PIE, this will cause problems as the main program itself will go the memory location that allows very little heap. This fixes the loader to detect PIE application by checking if elf_interpreter is requested, and loads them to beginning of the address space instead of the specially crafted place for elf interpreter. Signed-off-by: Timo Teräs --- fs/binfmt_elf.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 100edcc..1161e5d 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -802,6 +802,10 @@ static int load_elf_binary(struct linux_binprm *bprm) * default mmap base, as well as whatever program they * might try to exec. This is because the brk will * follow the loader, and is not movable. */ + if (elf_interpreter) + load_bias = 0x00400000UL; + else + load_bias = ELF_ET_DYN_BASE; #ifdef CONFIG_ARCH_BINFMT_ELF_RANDOMIZE_PIE /* Memory randomization might have been switched off * in runtime via sysctl or explicit setting of @@ -810,13 +814,14 @@ static int load_elf_binary(struct linux_binprm *bprm) * load_bias value in order to establish proper * non-randomized mappings. */ - if (current->flags & PF_RANDOMIZE) - load_bias = 0; - else - load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr); -#else - load_bias = ELF_PAGESTART(ELF_ET_DYN_BASE - vaddr); + if (current->flags & PF_RANDOMIZE) { + if (elf_interpreter) + load_bias += (get_random_int() & STACK_RND_MASK) << PAGE_SHIFT; + else + load_bias = 0; + } #endif + load_bias = ELF_PAGESTART(vaddr + load_bias); } error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt, -- 1.8.4