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Merge tag 'fsnotify_for_v5.13-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify fixes from Jan Kara:
 "A fix for permission checking with fanotify unpriviledged groups.

  Also there's a small update in MAINTAINERS file for fanotify"

* tag 'fsnotify_for_v5.13-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: fix permission model of unprivileged group
  MAINTAINERS: Add Matthew Bobrowski as a reviewer
This commit is contained in:
Linus Torvalds 2021-05-31 05:52:22 -10:00
commit 36c795513a
4 changed files with 30 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

1
MAINTAINERS
View file

@ -6945,6 +6945,7 @@ F: net/core/failover.c
FANOTIFY
M: Jan Kara <jack@suse.cz>
R: Amir Goldstein <amir73il@gmail.com>
R: Matthew Bobrowski <repnop@google.com>
L: linux-fsdevel@vger.kernel.org
S: Maintained
F: fs/notify/fanotify/

30
fs/notify/fanotify/fanotify_user.c
View file

@ -424,11 +424,18 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
* events generated by the listener process itself, without disclosing
* the pids of other processes.
*/
if (!capable(CAP_SYS_ADMIN) &&
if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
task_tgid(current) != event->pid)
metadata.pid = 0;
if (path && path->mnt && path->dentry) {
/*
* For now, fid mode is required for an unprivileged listener and
* fid mode does not report fd in events. Keep this check anyway
* for safety in case fid mode requirement is relaxed in the future
* to allow unprivileged listener to get events with no fd and no fid.
*/
if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
path && path->mnt && path->dentry) {
fd = create_fd(group, path, &f);
if (fd < 0)
return fd;
@ -1040,6 +1047,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
int f_flags, fd;
unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
unsigned int class = flags & FANOTIFY_CLASS_BITS;
unsigned int internal_flags = 0;
pr_debug("%s: flags=%x event_f_flags=%x\n",
__func__, flags, event_f_flags);
@ -1053,6 +1061,13 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
*/
if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) || !fid_mode)
return -EPERM;
/*
* Setting the internal flag FANOTIFY_UNPRIV on the group
* prevents setting mount/filesystem marks on this group and
* prevents reporting pid and open fd in events.
*/
internal_flags |= FANOTIFY_UNPRIV;
}
#ifdef CONFIG_AUDITSYSCALL
@ -1105,7 +1120,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
goto out_destroy_group;
}
group->fanotify_data.flags = flags;
group->fanotify_data.flags = flags | internal_flags;
group->memcg = get_mem_cgroup_from_mm(current->mm);
group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
@ -1305,11 +1320,13 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
group = f.file->private_data;
/*
* An unprivileged user is not allowed to watch a mount point nor
* a filesystem.
* An unprivileged user is not allowed to setup mount nor filesystem
* marks. This also includes setting up such marks by a group that
* was initialized by an unprivileged user.
*/
ret = -EPERM;
if (!capable(CAP_SYS_ADMIN) &&
if ((!capable(CAP_SYS_ADMIN) ||
FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV)) &&
mark_type != FAN_MARK_INODE)
goto fput_and_out;
@ -1460,6 +1477,7 @@ static int __init fanotify_user_setup(void)
max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
FANOTIFY_DEFAULT_MAX_USER_MARKS);
BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10);
BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9);

2
fs/notify/fdinfo.c
View file

@ -144,7 +144,7 @@ void fanotify_show_fdinfo(struct seq_file *m, struct file *f)
struct fsnotify_group *group = f->private_data;
seq_printf(m, "fanotify flags:%x event-flags:%x\n",
group->fanotify_data.flags,
group->fanotify_data.flags & FANOTIFY_INIT_FLAGS,
group->fanotify_data.f_flags);
show_fdinfo(m, f, fanotify_fdinfo);

4
include/linux/fanotify.h
View file

@ -51,6 +51,10 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
#define FANOTIFY_INIT_FLAGS (FANOTIFY_ADMIN_INIT_FLAGS | \
FANOTIFY_USER_INIT_FLAGS)
/* Internal group flags */
#define FANOTIFY_UNPRIV 0x80000000
#define FANOTIFY_INTERNAL_GROUP_FLAGS (FANOTIFY_UNPRIV)
#define FANOTIFY_MARK_TYPE_BITS (FAN_MARK_INODE | FAN_MARK_MOUNT | \
FAN_MARK_FILESYSTEM)