* [PATCH 1/2] mount: Support "nosymfollow" in new mount api
2021-06-01 13:55 [PATCH 0/2] mount: add "nosymfollow" support to new mount api Christian Brauner
@ 2021-06-01 13:55 ` Christian Brauner
2021-06-17 19:03 ` Ross Zwisler
2021-06-01 13:55 ` [PATCH 2/2] tests: test MOUNT_ATTR_NOSYMFOLLOW with mount_setattr() Christian Brauner
1 sibling, 1 reply; 5+ messages in thread
From: Christian Brauner @ 2021-06-01 13:55 UTC (permalink / raw)
To: linux-fsdevel
Cc: Christoph Hellwig, Al Viro, Mattias Nissler, Aleksa Sarai,
Ross Zwisler, Christian Brauner
From: Christian Brauner <christian.brauner@ubuntu.com>
Commit dab741e0e02b ("Add a "nosymfollow" mount option.") added support
for the "nosymfollow" mount option allowing to block following symlinks
when resolving paths. The mount option so far was only available in the
old mount api. Make it available in the new mount api as well. Bonus is
that it can be applied to a whole subtree not just a single mount.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mattias Nissler <mnissler@chromium.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <zwisler@google.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
fs/namespace.c | 9 ++++++---
include/uapi/linux/mount.h | 1 +
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index c3f1a78ba369..ab4174a3c802 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3464,9 +3464,10 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
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;
}
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index e6524ead2b7b..dd7a166fdf9c 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -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()
--
2.27.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/2] tests: test MOUNT_ATTR_NOSYMFOLLOW with mount_setattr()
2021-06-01 13:55 [PATCH 0/2] mount: add "nosymfollow" support to new mount api Christian Brauner
2021-06-01 13:55 ` [PATCH 1/2] mount: Support "nosymfollow" in " Christian Brauner
@ 2021-06-01 13:55 ` Christian Brauner
2021-06-17 19:03 ` Ross Zwisler
1 sibling, 1 reply; 5+ messages in thread
From: Christian Brauner @ 2021-06-01 13:55 UTC (permalink / raw)
To: linux-fsdevel
Cc: Christoph Hellwig, Al Viro, Mattias Nissler, Aleksa Sarai,
Ross Zwisler, Christian Brauner
From: Christian Brauner <christian.brauner@ubuntu.com>
Add tests to verify that MOUNT_ATTR_NOSYMFOLLOW is honored.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Mattias Nissler <mnissler@chromium.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Ross Zwisler <zwisler@google.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
.../mount_setattr/mount_setattr_test.c | 88 ++++++++++++++++++-
1 file changed, 85 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/mount_setattr/mount_setattr_test.c b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
index 4e94e566e040..f31205f04ee0 100644
--- a/tools/testing/selftests/mount_setattr/mount_setattr_test.c
+++ b/tools/testing/selftests/mount_setattr/mount_setattr_test.c
@@ -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
--
2.27.0
^ permalink raw reply related [flat|nested] 5+ messages in thread