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b9f5ce27c8
Introduce the LANDLOCK_ACCESS_FS_TRUNCATE flag for file truncation. This flag hooks into the path_truncate, file_truncate and file_alloc_security LSM hooks and covers file truncation using truncate(2), ftruncate(2), open(2) with O_TRUNC, as well as creat(). This change also increments the Landlock ABI version, updates corresponding selftests, and updates code documentation to document the flag. In security/security.c, allocate security blobs at pointer-aligned offsets. This fixes the problem where one LSM's security blob can shift another LSM's security blob to an unaligned address (reported by Nathan Chancellor). The following operations are restricted: open(2): requires the LANDLOCK_ACCESS_FS_TRUNCATE right if a file gets implicitly truncated as part of the open() (e.g. using O_TRUNC). Notable special cases: * open(..., O_RDONLY|O_TRUNC) can truncate files as well in Linux * open() with O_TRUNC does *not* need the TRUNCATE right when it creates a new file. truncate(2) (on a path): requires the LANDLOCK_ACCESS_FS_TRUNCATE right. ftruncate(2) (on a file): requires that the file had the TRUNCATE right when it was previously opened. File descriptors acquired by other means than open(2) (e.g. memfd_create(2)) continue to support truncation with ftruncate(2). Cc: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Günther Noack <gnoack3000@gmail.com> Acked-by: Paul Moore <paul@paul-moore.com> (LSM) Link: https://lore.kernel.org/r/20221018182216.301684-5-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün <mic@digikod.net>
41 lines
996 B
C
41 lines
996 B
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Landlock LSM - Security framework setup
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*
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* Copyright © 2016-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2018-2020 ANSSI
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*/
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#include <linux/init.h>
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#include <linux/lsm_hooks.h>
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#include "common.h"
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#include "cred.h"
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#include "fs.h"
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#include "ptrace.h"
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#include "setup.h"
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bool landlock_initialized __lsm_ro_after_init = false;
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struct lsm_blob_sizes landlock_blob_sizes __lsm_ro_after_init = {
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.lbs_cred = sizeof(struct landlock_cred_security),
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.lbs_file = sizeof(struct landlock_file_security),
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.lbs_inode = sizeof(struct landlock_inode_security),
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.lbs_superblock = sizeof(struct landlock_superblock_security),
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};
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static int __init landlock_init(void)
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{
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landlock_add_cred_hooks();
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landlock_add_ptrace_hooks();
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landlock_add_fs_hooks();
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landlock_initialized = true;
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pr_info("Up and running.\n");
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return 0;
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}
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DEFINE_LSM(LANDLOCK_NAME) = {
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.name = LANDLOCK_NAME,
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.init = landlock_init,
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.blobs = &landlock_blob_sizes,
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};
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