Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752526AbaLAGJI (ORCPT ); Mon, 1 Dec 2014 01:09:08 -0500 Received: from mail-pa0-f48.google.com ([209.85.220.48]:44422 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751243AbaLAGJH (ORCPT ); Mon, 1 Dec 2014 01:09:07 -0500 From: Jungseung Lee To: Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: Jungseung Lee Subject: [RFC PATCHv2] fs/binfmt_elf.c: fix internal inconsistency relating to vma dump size Date: Mon, 1 Dec 2014 15:08:58 +0900 Message-Id: <1417414138-5927-1-git-send-email-js07.lee@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org vma_dump_size() has been used several times on actual dumper and it is supposed to return the same value for the same vma. But vma_dump_size() could return different values for same vma. The known problem case is concurrent shared memory removal. If a vma is used for a shared memory and that shared memory is removed between writing program header and dumping vma memory, this will result in a dump file which is internally consistent. To fix the problem, we set baseline to get dump size and store the size into vma_filesz and always use the same vma dump size which is stored in vma_filsz. The consistnecy with reality is not actually guranteed, but it's tolerable since that is fully consistent with base line. Signed-off-by: Jungseung Lee --- fs/binfmt_elf.c | 40 ++++++++++++++++++++++------------------ 1 file changed, 22 insertions(+), 18 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index d8fc060..3a6175f 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1994,18 +1994,6 @@ static void fill_extnum_info(struct elfhdr *elf, struct elf_shdr *shdr4extnum, shdr4extnum->sh_info = segs; } -static size_t elf_core_vma_data_size(struct vm_area_struct *gate_vma, - unsigned long mm_flags) -{ - struct vm_area_struct *vma; - size_t size = 0; - - for (vma = first_vma(current, gate_vma); vma != NULL; - vma = next_vma(vma, gate_vma)) - size += vma_dump_size(vma, mm_flags); - return size; -} - /* * Actual dumper * @@ -2017,7 +2005,8 @@ static int elf_core_dump(struct coredump_params *cprm) { int has_dumped = 0; mm_segment_t fs; - int segs; + int segs, i; + size_t vma_data_size = 0; struct vm_area_struct *vma, *gate_vma; struct elfhdr *elf = NULL; loff_t offset = 0, dataoff; @@ -2026,6 +2015,7 @@ static int elf_core_dump(struct coredump_params *cprm) struct elf_shdr *shdr4extnum = NULL; Elf_Half e_phnum; elf_addr_t e_shoff; + elf_addr_t *vma_filesz = NULL; /* * We no longer stop all VM operations. @@ -2093,7 +2083,20 @@ static int elf_core_dump(struct coredump_params *cprm) dataoff = offset = roundup(offset, ELF_EXEC_PAGESIZE); - offset += elf_core_vma_data_size(gate_vma, cprm->mm_flags); + vma_filesz = kmalloc_array(segs - 1, sizeof(*vma_filesz), GFP_KERNEL); + if (!vma_filesz) + goto end_coredump; + + for (i = 0, vma = first_vma(current, gate_vma); vma != NULL; + vma = next_vma(vma, gate_vma)) { + unsigned long dump_size; + + dump_size = vma_dump_size(vma, cprm->mm_flags); + vma_filesz[i++] = dump_size; + vma_data_size += dump_size; + } + + offset += vma_data_size; offset += elf_core_extra_data_size(); e_shoff = offset; @@ -2113,7 +2116,7 @@ static int elf_core_dump(struct coredump_params *cprm) goto end_coredump; /* Write program headers for segments dump */ - for (vma = first_vma(current, gate_vma); vma != NULL; + for (i = 0, vma = first_vma(current, gate_vma); vma != NULL; vma = next_vma(vma, gate_vma)) { struct elf_phdr phdr; @@ -2121,7 +2124,7 @@ static int elf_core_dump(struct coredump_params *cprm) phdr.p_offset = offset; phdr.p_vaddr = vma->vm_start; phdr.p_paddr = 0; - phdr.p_filesz = vma_dump_size(vma, cprm->mm_flags); + phdr.p_filesz = vma_filesz[i++]; phdr.p_memsz = vma->vm_end - vma->vm_start; offset += phdr.p_filesz; phdr.p_flags = vma->vm_flags & VM_READ ? PF_R : 0; @@ -2149,12 +2152,12 @@ static int elf_core_dump(struct coredump_params *cprm) if (!dump_skip(cprm, dataoff - cprm->written)) goto end_coredump; - for (vma = first_vma(current, gate_vma); vma != NULL; + for (i = 0, vma = first_vma(current, gate_vma); vma != NULL; vma = next_vma(vma, gate_vma)) { unsigned long addr; unsigned long end; - end = vma->vm_start + vma_dump_size(vma, cprm->mm_flags); + end = vma->vm_start + vma_filesz[i++]; for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) { struct page *page; @@ -2187,6 +2190,7 @@ end_coredump: cleanup: free_note_info(&info); kfree(shdr4extnum); + kfree(vma_filesz); kfree(phdr4note); kfree(elf); out: -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/