From patchwork Tue Apr 5 07:26:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 556767 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 9BAC2C41535 for ; Tue, 5 Apr 2022 11:47:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381615AbiDELqj (ORCPT ); Tue, 5 Apr 2022 07:46:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354981AbiDEKQu (ORCPT ); Tue, 5 Apr 2022 06:16:50 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8789DE9F; Tue, 5 Apr 2022 03:04:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1E0546174B; Tue, 5 Apr 2022 10:04:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32017C385A2; Tue, 5 Apr 2022 10:04:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649153062; bh=z3BpInOZg7lcxumibtyoEA2UOYtY6znbUUxMJ1KDSLk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qcKRcJdX+ymKjtFLlxmtWtPzKKrsMRvLPwF/zEIk08ieiVfzdXOrcudTzLm7Mtapv vq+AN7IeMQlMDqrMIRGdefkNlow2K+QlIGywoAwIIBUcme0749sXJYfVNBUZwbuyN2 z19DOl+ANRsoqkFWGpUtwAhpD00IZlnee6n52TVo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Bill Messmer , Jann Horn , Kees Cook Subject: [PATCH 5.10 089/599] coredump: Also dump first pages of non-executable ELF libraries Date: Tue, 5 Apr 2022 09:26:23 +0200 Message-Id: <20220405070301.478765187@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070258.802373272@linuxfoundation.org> References: <20220405070258.802373272@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jann Horn commit 84158b7f6a0624b81800b4e7c90f7fb7fdecf66c upstream. When I rewrote the VMA dumping logic for coredumps, I changed it to recognize ELF library mappings based on the file being executable instead of the mapping having an ELF header. But turns out, distros ship many ELF libraries as non-executable, so the heuristic goes wrong... Restore the old behavior where FILTER(ELF_HEADERS) dumps the first page of any offset-0 readable mapping that starts with the ELF magic. This fix is technically layer-breaking a bit, because it checks for something ELF-specific in fs/coredump.c; but since we probably want to share this between standard ELF and FDPIC ELF anyway, I guess it's fine? And this also keeps the change small for backporting. Cc: stable@vger.kernel.org Fixes: 429a22e776a2 ("coredump: rework elf/elf_fdpic vma_dump_size() into common helper") Reported-by: Bill Messmer Signed-off-by: Jann Horn Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220126025739.2014888-1-jannh@google.com Signed-off-by: Greg Kroah-Hartman --- fs/coredump.c | 39 ++++++++++++++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 5 deletions(-) --- a/fs/coredump.c +++ b/fs/coredump.c @@ -41,6 +41,7 @@ #include #include #include +#include #include #include @@ -969,6 +970,8 @@ static bool always_dump_vma(struct vm_ar return false; } +#define DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER 1 + /* * Decide how much of @vma's contents should be included in a core dump. */ @@ -1028,9 +1031,20 @@ static unsigned long vma_dump_size(struc * dump the first page to aid in determining what was mapped here. */ if (FILTER(ELF_HEADERS) && - vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ) && - (READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0) - return PAGE_SIZE; + vma->vm_pgoff == 0 && (vma->vm_flags & VM_READ)) { + if ((READ_ONCE(file_inode(vma->vm_file)->i_mode) & 0111) != 0) + return PAGE_SIZE; + + /* + * ELF libraries aren't always executable. + * We'll want to check whether the mapping starts with the ELF + * magic, but not now - we're holding the mmap lock, + * so copy_from_user() doesn't work here. + * Use a placeholder instead, and fix it up later in + * dump_vma_snapshot(). + */ + return DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER; + } #undef FILTER @@ -1105,8 +1119,6 @@ int dump_vma_snapshot(struct coredump_pa m->end = vma->vm_end; m->flags = vma->vm_flags; m->dump_size = vma_dump_size(vma, cprm->mm_flags); - - vma_data_size += m->dump_size; } mmap_write_unlock(mm); @@ -1116,6 +1128,23 @@ int dump_vma_snapshot(struct coredump_pa return -EFAULT; } + for (i = 0; i < *vma_count; i++) { + struct core_vma_metadata *m = (*vma_meta) + i; + + if (m->dump_size == DUMP_SIZE_MAYBE_ELFHDR_PLACEHOLDER) { + char elfmag[SELFMAG]; + + if (copy_from_user(elfmag, (void __user *)m->start, SELFMAG) || + memcmp(elfmag, ELFMAG, SELFMAG) != 0) { + m->dump_size = 0; + } else { + m->dump_size = PAGE_SIZE; + } + } + + vma_data_size += m->dump_size; + } + *vma_data_size_ptr = vma_data_size; return 0; }