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fs.mount_setattr.nosymfollow.v5.14 

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Merge tag 'fs.mount_setattr.nosymfollow.v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull mount_setattr updates from Christian Brauner:
 "A few releases ago the old mount API gained support for a mount
  options which prevents following symlinks on a given mount. This adds
  support for it in the new mount api through the MOUNT_ATTR_NOSYMFOLLOW
  flag via mount_setattr() and fsmount(). With mount_setattr() that flag
  can even be applied recursively.

  There's an additional ack from Ross Zwisler who originally authored
  the nosymfollow patch. As I've already had the patches in my for-next
  I didn't add his ack explicitly"

* tag 'fs.mount_setattr.nosymfollow.v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  tests: test MOUNT_ATTR_NOSYMFOLLOW with mount_setattr()
  mount: Support "nosymfollow" in new mount api
This commit is contained in:
Linus Torvalds 2021-06-29 20:07:06 -07:00
parent 65090f30ab 5990b5d770
commit 30d1a556a9
3 changed files with 92 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
fs/namespace.c
View File

@ -3464,9 +3464,10 @@ out_type:
return ret;
}
#define FSMOUNT_VALID_FLAGS \
(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME)
#define FSMOUNT_VALID_FLAGS \
(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
MOUNT_ATTR_NOSYMFOLLOW)
#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
@ -3487,6 +3488,8 @@ static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
mnt_flags |= MNT_NOEXEC;
if (attr_flags & MOUNT_ATTR_NODIRATIME)
mnt_flags |= MNT_NODIRATIME;
if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
mnt_flags |= MNT_NOSYMFOLLOW;
return mnt_flags;
}

1
include/uapi/linux/mount.h
View File

@ -120,6 +120,7 @@ enum fsconfig_command {
#define MOUNT_ATTR_STRICTATIME 0x00000020 /* - Always perform atime updates */
#define MOUNT_ATTR_NODIRATIME 0x00000080 /* Do not update directory access times */
#define MOUNT_ATTR_IDMAP 0x00100000 /* Idmap mount to @userns_fd in struct mount_attr. */
#define MOUNT_ATTR_NOSYMFOLLOW 0x00200000 /* Do not follow symlinks */
/*
* mount_setattr()

88
tools/testing/selftests/mount_setattr/mount_setattr_test.c
View File

@ -136,6 +136,10 @@ struct mount_attr {
#define MOUNT_ATTR_IDMAP 0x00100000
#endif
#ifndef MOUNT_ATTR_NOSYMFOLLOW
#define MOUNT_ATTR_NOSYMFOLLOW 0x00200000
#endif
static inline int sys_mount_setattr(int dfd, const char *path, unsigned int flags,
struct mount_attr *attr, size_t size)
{
@ -235,6 +239,10 @@ static int prepare_unpriv_mountns(void)
return 0;
}
#ifndef ST_NOSYMFOLLOW
#define ST_NOSYMFOLLOW 0x2000 /* do not follow symlinks */
#endif
static int read_mnt_flags(const char *path)
{
int ret;
@ -245,9 +253,9 @@ static int read_mnt_flags(const char *path)
if (ret != 0)
return -EINVAL;
if (stat.f_flag &
~(ST_RDONLY | ST_NOSUID | ST_NODEV | ST_NOEXEC | ST_NOATIME |
ST_NODIRATIME | ST_RELATIME | ST_SYNCHRONOUS | ST_MANDLOCK))
if (stat.f_flag & ~(ST_RDONLY | ST_NOSUID | ST_NODEV | ST_NOEXEC |
ST_NOATIME | ST_NODIRATIME | ST_RELATIME |
ST_SYNCHRONOUS | ST_MANDLOCK | ST_NOSYMFOLLOW))
return -EINVAL;
mnt_flags = 0;
@ -269,6 +277,8 @@ static int read_mnt_flags(const char *path)
mnt_flags |= MS_SYNCHRONOUS;
if (stat.f_flag & ST_MANDLOCK)
mnt_flags |= ST_MANDLOCK;
if (stat.f_flag & ST_NOSYMFOLLOW)
mnt_flags |= ST_NOSYMFOLLOW;
return mnt_flags;
}
@ -368,8 +378,13 @@ static bool mount_setattr_supported(void)
FIXTURE(mount_setattr) {
};
#define NOSYMFOLLOW_TARGET "/mnt/A/AA/data"
#define NOSYMFOLLOW_SYMLINK "/mnt/A/AA/symlink"
FIXTURE_SETUP(mount_setattr)
{
int fd = -EBADF;
if (!mount_setattr_supported())
SKIP(return, "mount_setattr syscall not supported");
@ -412,6 +427,11 @@ FIXTURE_SETUP(mount_setattr)
ASSERT_EQ(mount("testing", "/tmp/B/BB", "devpts",
MS_RELATIME | MS_NOEXEC | MS_RDONLY, 0), 0);
fd = creat(NOSYMFOLLOW_TARGET, O_RDWR | O_CLOEXEC);
ASSERT_GT(fd, 0);
ASSERT_EQ(symlink(NOSYMFOLLOW_TARGET, NOSYMFOLLOW_SYMLINK), 0);
ASSERT_EQ(close(fd), 0);
}
FIXTURE_TEARDOWN(mount_setattr)
@ -1421,4 +1441,66 @@ TEST_F(mount_setattr_idmapped, idmap_mount_tree_invalid)
ASSERT_EQ(expected_uid_gid(open_tree_fd, "B/BB/b", 0, 0, 0), 0);
}
TEST_F(mount_setattr, mount_attr_nosymfollow)
{
int fd;
unsigned int old_flags = 0, new_flags = 0, expected_flags = 0;
struct mount_attr attr = {
.attr_set = MOUNT_ATTR_NOSYMFOLLOW,
};
if (!mount_setattr_supported())
SKIP(return, "mount_setattr syscall not supported");
fd = open(NOSYMFOLLOW_SYMLINK, O_RDWR | O_CLOEXEC);
ASSERT_GT(fd, 0);
ASSERT_EQ(close(fd), 0);
old_flags = read_mnt_flags("/mnt/A");
ASSERT_GT(old_flags, 0);
ASSERT_EQ(sys_mount_setattr(-1, "/mnt/A", AT_RECURSIVE, &attr, sizeof(attr)), 0);
expected_flags = old_flags;
expected_flags |= ST_NOSYMFOLLOW;
new_flags = read_mnt_flags("/mnt/A");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA/B");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA/B/BB");
ASSERT_EQ(new_flags, expected_flags);
fd = open(NOSYMFOLLOW_SYMLINK, O_RDWR | O_CLOEXEC);
ASSERT_LT(fd, 0);
ASSERT_EQ(errno, ELOOP);
attr.attr_set &= ~MOUNT_ATTR_NOSYMFOLLOW;
attr.attr_clr |= MOUNT_ATTR_NOSYMFOLLOW;
ASSERT_EQ(sys_mount_setattr(-1, "/mnt/A", AT_RECURSIVE, &attr, sizeof(attr)), 0);
expected_flags &= ~ST_NOSYMFOLLOW;
new_flags = read_mnt_flags("/mnt/A");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA/B");
ASSERT_EQ(new_flags, expected_flags);
new_flags = read_mnt_flags("/mnt/A/AA/B/BB");
ASSERT_EQ(new_flags, expected_flags);
fd = open(NOSYMFOLLOW_SYMLINK, O_RDWR | O_CLOEXEC);
ASSERT_GT(fd, 0);
ASSERT_EQ(close(fd), 0);
}
TEST_HARNESS_MAIN