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Landlock fix for v6.10-rc2

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Merge tag 'landlock-6.10-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux

Pull landlock fix from Mickaël Salaün:
 "This fixes a wrong path walk triggered by syzkaller"

* tag 'landlock-6.10-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux:
  selftests/landlock: Add layout1.refer_mount_root
  landlock: Fix d_parent walk
This commit is contained in:
Linus Torvalds 2024-06-01 08:28:24 -07:00
commit d9aab0b1c9
2 changed files with 56 additions and 2 deletions
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13
security/landlock/fs.c
View File

@ -1110,6 +1110,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
bool allow_parent1, allow_parent2;
access_mask_t access_request_parent1, access_request_parent2;
struct path mnt_dir;
struct dentry *old_parent;
layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {},
layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {};
@ -1157,9 +1158,17 @@ static int current_check_refer_path(struct dentry *const old_dentry,
mnt_dir.mnt = new_dir->mnt;
mnt_dir.dentry = new_dir->mnt->mnt_root;
/*
* old_dentry may be the root of the common mount point and
* !IS_ROOT(old_dentry) at the same time (e.g. with open_tree() and
* OPEN_TREE_CLONE). We do not need to call dget(old_parent) because
* we keep a reference to old_dentry.
*/
old_parent = (old_dentry == mnt_dir.dentry) ? old_dentry :
old_dentry->d_parent;
/* new_dir->dentry is equal to new_dentry->d_parent */
allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry,
old_dentry->d_parent,
allow_parent1 = collect_domain_accesses(dom, mnt_dir.dentry, old_parent,
&layer_masks_parent1);
allow_parent2 = collect_domain_accesses(
dom, mnt_dir.dentry, new_dir->dentry, &layer_masks_parent2);

45
tools/testing/selftests/landlock/fs_test.c
View File

@ -35,6 +35,7 @@
* See https://sourceware.org/glibc/wiki/Synchronizing_Headers.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include "common.h"
@ -47,6 +48,13 @@ int renameat2(int olddirfd, const char *oldpath, int newdirfd,
}
#endif
#ifndef open_tree
int open_tree(int dfd, const char *filename, unsigned int flags)
{
return syscall(__NR_open_tree, dfd, filename, flags);
}
#endif
#ifndef RENAME_EXCHANGE
#define RENAME_EXCHANGE (1 << 1)
#endif
@ -2400,6 +2408,43 @@ TEST_F_FORK(layout1, refer_denied_by_default4)
layer_dir_s1d1_refer);
}
/*
* Tests walking through a denied root mount.
*/
TEST_F_FORK(layout1, refer_mount_root_deny)
{
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_MAKE_DIR,
};
int root_fd, ruleset_fd;
/* Creates a mount object from a non-mount point. */
set_cap(_metadata, CAP_SYS_ADMIN);
root_fd =
open_tree(AT_FDCWD, dir_s1d1,
AT_EMPTY_PATH | OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
clear_cap(_metadata, CAP_SYS_ADMIN);
ASSERT_LE(0, root_fd);
ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
EXPECT_EQ(0, close(ruleset_fd));
/* Link denied by Landlock: EACCES. */
EXPECT_EQ(-1, linkat(root_fd, ".", root_fd, "does_not_exist", 0));
EXPECT_EQ(EACCES, errno);
/* renameat2() always returns EBUSY. */
EXPECT_EQ(-1, renameat2(root_fd, ".", root_fd, "does_not_exist", 0));
EXPECT_EQ(EBUSY, errno);
EXPECT_EQ(0, close(root_fd));
}
TEST_F_FORK(layout1, reparent_link)
{
const struct rule layer1[] = {