From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Baoquan He To: linux-kernel@vger.kernel.org Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, oleg@redhat.com, mhocko@kerne.org, keescook@chromium.org, jkosina@suse.cz, mingo@elte.hu, torvalds@linux-foundation.org, Baoquan He Subject: [PATCH 3/3] binfmt_elf: Search an unmapped area with total_size but not map the whole image Date: Fri, 6 Oct 2017 11:37:58 +0800 Message-Id: <1507261078-23615-4-git-send-email-bhe@redhat.com> In-Reply-To: <1507261078-23615-1-git-send-email-bhe@redhat.com> References: <1507261078-23615-1-git-send-email-bhe@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: In elf_map(), we can search an unmapped area for the whole image of dynamic loader with total_size, then map the first PT_LOAD segment with its own size. But not map the while image, then unmap the remainder at the end. And also update the code comment in elf_map() accordingly. Signed-off-by: Baoquan He --- fs/binfmt_elf.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index d7a8a53a6f18..bebb9f2c934e 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -357,20 +357,23 @@ static unsigned long elf_map(struct file *filep, unsigned long addr, return addr; /* - * total_size is the size of the ELF (interpreter) image. - * The _first_ mmap needs to know the full size, otherwise - * randomization might put this image into an overlapping - * position with the ELF binary image. (since size < total_size) - * So we first map the 'big' image - and unmap the remainder at - * the end. (which unmap is needed for ELF images with holes.) + * total_size is the size of the ELF (interpreter) image if non-zero. + * It gets value either in load_elf_interp(), or in load_elf_binary() + * for "./ld.so someprog" testing. The _first_ mmap needs to know the + * full size, otherwise the first PT_LOAD segment is mapped below + * mm->mmap_base, the subsequent PT_LOAD segment(s) end up being mapped + * above mm->mmap_base into the area that is supposed to be the "gap" + * between the stack and the binary. So we search an unmapped area of + * total_size big, then use the found address as hint to do mmap. */ if (total_size) { total_size = ELF_PAGEALIGN(total_size); - map_addr = vm_mmap(filep, addr, total_size, prot, flags, off); - if (!BAD_ADDR(map_addr)) - vm_munmap(map_addr+size, total_size-size); - } else - map_addr = vm_mmap(filep, addr, size, prot, flags, off); + addr = get_unmapped_area(file, addr, total_size, off, flags); + if (offset_in_page(addr)) + return addr; + } + + map_addr = vm_mmap(filep, addr, size, prot, flags, off); return(map_addr); } -- 2.5.5