From patchwork Mon Jan 31 18:47:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 12731028 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3696CC433EF for ; Mon, 31 Jan 2022 18:48:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357895AbiAaSr7 (ORCPT ); Mon, 31 Jan 2022 13:47:59 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:59644 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357716AbiAaSro (ORCPT ); Mon, 31 Jan 2022 13:47:44 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]:42370) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nEbiI-00HXSu-1F; Mon, 31 Jan 2022 11:47:43 -0700 Received: from ip68-110-24-146.om.om.cox.net ([68.110.24.146]:56392 helo=email.froward.int.ebiederm.org.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nEbiG-007mQf-FJ; Mon, 31 Jan 2022 11:47:41 -0700 From: "Eric W. Biederman" To: Jann Horn Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Viro , Denys Vlasenko , Kees Cook , Vlastimil Babka , "Liam R . Howlett" References: <20220131153740.2396974-1-willy@infradead.org> <871r0nriy4.fsf@email.froward.int.ebiederm.org> <877dafq3bw.fsf@email.froward.int.ebiederm.org> <87bkzroica.fsf_-_@email.froward.int.ebiederm.org> Date: Mon, 31 Jan 2022 12:47:34 -0600 In-Reply-To: <87bkzroica.fsf_-_@email.froward.int.ebiederm.org> (Eric W. Biederman's message of "Mon, 31 Jan 2022 12:44:53 -0600") Message-ID: <87iltzn3nd.fsf_-_@email.froward.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1nEbiG-007mQf-FJ;;;mid=<87iltzn3nd.fsf_-_@email.froward.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.110.24.146;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX1/oGpZ9UFLzbnQWhkV7XiMYkWr0BtePZic= X-SA-Exim-Connect-IP: 68.110.24.146 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 5/5] coredump: Use the vma snapshot in fill_files_note X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Matthew Wilcox reported that there is a missing mmap_lock in file_files_note that could possibly lead to a user after free. Solve this by using the existing vma snapshot for consistency and to avoid the need to take the mmap_lock anywhere in the coredump code except for dump_vma_snapshot. Update the dump_vma_snapshot to capture vm_pgoff and vm_file that are neeeded by fill_files_note. Add free_vma_snapshot to free the captured values of vm_file. Reported-by: Matthew Wilcox Link: https://lkml.kernel.org/r/20220131153740.2396974-1-willy@infradead.org Cc: stable@vger.kernel.org Fixes: a07279c9a8cd ("binfmt_elf, binfmt_elf_fdpic: use a VMA list snapshot") Fixes: 2aa362c49c31 ("coredump: extend core dump note section to contain file names of mapped files") Signed-off-by: "Eric W. Biederman" --- fs/binfmt_elf.c | 19 ++++++++++--------- fs/coredump.c | 22 +++++++++++++++++++++- include/linux/coredump.h | 2 ++ 3 files changed, 33 insertions(+), 10 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 272032b1f9a2..5fcaa01d211e 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1619,14 +1619,14 @@ static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t *csigdata, * long file_ofs * followed by COUNT filenames in ASCII: "FILE1" NUL "FILE2" NUL... */ -static int fill_files_note(struct memelfnote *note) +static int fill_files_note(struct memelfnote *note, struct coredump_params *cprm) { struct mm_struct *mm = current->mm; - struct vm_area_struct *vma; unsigned count, size, names_ofs, remaining, n; user_long_t *data; user_long_t *start_end_ofs; char *name_base, *name_curpos; + int i; /* *Estimated* file count and total data size needed */ count = mm->map_count; @@ -1651,11 +1651,12 @@ static int fill_files_note(struct memelfnote *note) name_base = name_curpos = ((char *)data) + names_ofs; remaining = size - names_ofs; count = 0; - for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) { + for (i = 0; i < cprm->vma_count; i++) { + struct core_vma_metadata *m = &cprm->vma_meta[i]; struct file *file; const char *filename; - file = vma->vm_file; + file = m->file; if (!file) continue; filename = file_path(file, name_curpos, remaining); @@ -1675,9 +1676,9 @@ static int fill_files_note(struct memelfnote *note) memmove(name_curpos, filename, n); name_curpos += n; - *start_end_ofs++ = vma->vm_start; - *start_end_ofs++ = vma->vm_end; - *start_end_ofs++ = vma->vm_pgoff; + *start_end_ofs++ = m->start; + *start_end_ofs++ = m->end; + *start_end_ofs++ = m->pgoff; count++; } @@ -1887,7 +1888,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs, fill_auxv_note(&info->auxv, current->mm); info->size += notesize(&info->auxv); - if (fill_files_note(&info->files) == 0) + if (fill_files_note(&info->files, cprm) == 0) info->size += notesize(&info->files); return 1; @@ -2076,7 +2077,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs, fill_auxv_note(info->notes + 3, current->mm); info->numnote = 4; - if (fill_files_note(info->notes + info->numnote) == 0) { + if (fill_files_note(info->notes + info->numnote, cprm) == 0) { info->notes_files = info->notes + info->numnote; info->numnote++; } diff --git a/fs/coredump.c b/fs/coredump.c index c5e7d63525c6..6a97a8ea7295 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -54,6 +54,7 @@ #include static bool dump_vma_snapshot(struct coredump_params *cprm); +static void free_vma_snapshot(struct coredump_params *cprm); static int core_uses_pid; static unsigned int core_pipe_limit; @@ -764,7 +765,7 @@ void do_coredump(const kernel_siginfo_t *siginfo) dump_emit(&cprm, "", 1); } file_end_write(cprm.file); - kvfree(cprm.vma_meta); + free_vma_snapshot(&cprm); } if (ispipe && core_pipe_limit) wait_for_dump_helpers(cprm.file); @@ -1085,6 +1086,20 @@ static struct vm_area_struct *next_vma(struct vm_area_struct *this_vma, return gate_vma; } +static void free_vma_snapshot(struct coredump_params *cprm) +{ + if (cprm->vma_meta) { + int i; + for (i = 0; i < cprm->vma_count; i++) { + struct file *file = cprm->vma_meta[i].file; + if (file) + fput(file); + } + kvfree(cprm->vma_meta); + cprm->vma_meta = NULL; + } +} + /* * Under the mmap_lock, take a snapshot of relevant information about the task's * VMAs. @@ -1121,6 +1136,11 @@ static bool dump_vma_snapshot(struct coredump_params *cprm) m->end = vma->vm_end; m->flags = vma->vm_flags; m->dump_size = vma_dump_size(vma, cprm->mm_flags); + m->pgoff = vma->vm_pgoff; + + m->file = vma->vm_file; + if (m->file) + get_file(m->file); cprm->vma_data_size += m->dump_size; } diff --git a/include/linux/coredump.h b/include/linux/coredump.h index 7d05370e555e..08a1d3e7e46d 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h @@ -12,6 +12,8 @@ struct core_vma_metadata { unsigned long start, end; unsigned long flags; unsigned long dump_size; + unsigned long pgoff; + struct file *file; }; struct coredump_params {