linux-stable.git/fs/proc/base.c, branch v3.16.35

fs/proc, core/debug: Don't expose absolute kernel addresses via wchan

2015-12-13T17:49:51+00:00

commit b2f73922d119686323f14fbbe46587f863852328 upstream.

So the /proc/PID/stat 'wchan' field (the 30th field, which contains
the absolute kernel address of the kernel function a task is blocked in)
leaks absolute kernel addresses to unprivileged user-space:

        seq_put_decimal_ull(m, ' ', wchan);

The absolute address might also leak via /proc/PID/wchan as well, if
KALLSYMS is turned off or if the symbol lookup fails for some reason:

static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
                          struct pid *pid, struct task_struct *task)
{
        unsigned long wchan;
        char symname[KSYM_NAME_LEN];

        wchan = get_wchan(task);

        if (lookup_symbol_name(wchan, symname) < 0) {
                if (!ptrace_may_access(task, PTRACE_MODE_READ))
                        return 0;
                seq_printf(m, "%lu", wchan);
        } else {
                seq_printf(m, "%s", symname);
        }

        return 0;
}

This isn't ideal, because for example it trivially leaks the KASLR offset
to any local attacker:

  fomalhaut:~> printf "%016lx\n" $(cat /proc/$$/stat | cut -d' ' -f35)
  ffffffff8123b380

Most real-life uses of wchan are symbolic:

  ps -eo pid:10,tid:10,wchan:30,comm

and procps uses /proc/PID/wchan, not the absolute address in /proc/PID/stat:

  triton:~/tip> strace -f ps -eo pid:10,tid:10,wchan:30,comm 2>&1 | grep wchan | tail -1
  open("/proc/30833/wchan", O_RDONLY)     = 6

There's one compatibility quirk here: procps relies on whether the
absolute value is non-zero - and we can provide that functionality
by outputing "0" or "1" depending on whether the task is blocked
(whether there's a wchan address).

These days there appears to be very little legitimate reason
user-space would be interested in  the absolute address. The
absolute address is mostly historic: from the days when we
didn't have kallsyms and user-space procps had to do the
decoding itself via the System.map.

So this patch sets all numeric output to "0" or "1" and keeps only
symbolic output, in /proc/PID/wchan.

( The absolute sleep address can generally still be profiled via
  perf, by tasks with sufficient privileges. )

Reviewed-by: Thomas Gleixner 
Acked-by: Kees Cook 
Acked-by: Linus Torvalds 
Cc: Al Viro 
Cc: Alexander Potapenko 
Cc: Andrey Konovalov 
Cc: Andrey Ryabinin 
Cc: Andy Lutomirski 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Denys Vlasenko 
Cc: Dmitry Vyukov 
Cc: Kostya Serebryany 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Peter Zijlstra 
Cc: Sasha Levin 
Cc: kasan-dev 
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150930135917.GA3285@gmail.com
Signed-off-by: Ingo Molnar 
[ kamal: backport to 3.16-stable: proc_pid_wchan context ]
Signed-off-by: Kamal Mostafa 
Signed-off-by: Luis Henriques

userns: Add a knob to disable setgroups on a per user namespace basis

2015-01-15T10:43:58+00:00

commit 9cc46516ddf497ea16e8d7cb986ae03a0f6b92f8 upstream.

- Expose the knob to user space through a proc file /proc//setgroups

  A value of "deny" means the setgroups system call is disabled in the
  current processes user namespace and can not be enabled in the
  future in this user namespace.

  A value of "allow" means the segtoups system call is enabled.

- Descendant user namespaces inherit the value of setgroups from
  their parents.

- A proc file is used (instead of a sysctl) as sysctls currently do
  not allow checking the permissions at open time.

- Writing to the proc file is restricted to before the gid_map
  for the user namespace is set.

  This ensures that disabling setgroups at a user namespace
  level will never remove the ability to call setgroups
  from a process that already has that ability.

  A process may opt in to the setgroups disable for itself by
  creating, entering and configuring a user namespace or by calling
  setns on an existing user namespace with setgroups disabled.
  Processes without privileges already can not call setgroups so this
  is a noop.  Prodcess with privilege become processes without
  privilege when entering a user namespace and as with any other path
  to dropping privilege they would not have the ability to call
  setgroups.  So this remains within the bounds of what is possible
  without a knob to disable setgroups permanently in a user namespace.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Luis Henriques

Merge git://git.infradead.org/users/eparis/audit

2014-04-12T19:38:53+00:00

Pull audit updates from Eric Paris.

* git://git.infradead.org/users/eparis/audit: (28 commits)
  AUDIT: make audit_is_compat depend on CONFIG_AUDIT_COMPAT_GENERIC
  audit: renumber AUDIT_FEATURE_CHANGE into the 1300 range
  audit: do not cast audit_rule_data pointers pointlesly
  AUDIT: Allow login in non-init namespaces
  audit: define audit_is_compat in kernel internal header
  kernel: Use RCU_INIT_POINTER(x, NULL) in audit.c
  sched: declare pid_alive as inline
  audit: use uapi/linux/audit.h for AUDIT_ARCH declarations
  syscall_get_arch: remove useless function arguments
  audit: remove stray newline from audit_log_execve_info() audit_panic() call
  audit: remove stray newlines from audit_log_lost messages
  audit: include subject in login records
  audit: remove superfluous new- prefix in AUDIT_LOGIN messages
  audit: allow user processes to log from another PID namespace
  audit: anchor all pid references in the initial pid namespace
  audit: convert PPIDs to the inital PID namespace.
  pid: get pid_t ppid of task in init_pid_ns
  audit: rename the misleading audit_get_context() to audit_take_context()
  audit: Add generic compat syscall support
  audit: Add CONFIG_HAVE_ARCH_AUDITSYSCALL
  ...

fault-injection: set bounds on what /proc/self/make-it-fail accepts.

2014-04-07T23:36:10+00:00

/proc/self/make-it-fail is a boolean, but accepts any number, including
negative ones.  Change variable to unsigned, and cap upper bound at 1.

[akpm@linux-foundation.org: don't make make_it_fail unsigned]
Signed-off-by: Dave Jones 
Reviewed-by: Akinobu Mita 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

procfs: make /proc/*/pagemap 0400

2014-04-07T23:36:05+00:00

The /proc/*/pagemap contain sensitive information and currently its mode
is 0444.  Change this to 0400, so the VFS will prevent unprivileged
processes from getting file descriptors on arbitrary privileged
/proc/*/pagemap files.

This reduces the scope of address space leaking and bypasses by protecting
already running processes.

Signed-off-by: Djalal Harouni 
Acked-by: Kees Cook 
Acked-by: Andy Lutomirski 
Cc: Eric W. Biederman 
Cc: Al Viro 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

procfs: make /proc/*/{stack,syscall,personality} 0400

2014-04-07T23:36:04+00:00

These procfs files contain sensitive information and currently their
mode is 0444.  Change this to 0400, so the VFS will be able to block
unprivileged processes from getting file descriptors on arbitrary
privileged /proc/*/{stack,syscall,personality} files.

This reduces the scope of ASLR leaking and bypasses by protecting already
running processes.

Signed-off-by: Djalal Harouni 
Acked-by: Kees Cook 
Acked-by: Andy Lutomirski 
Cc: Eric W. Biederman 
Cc: Al Viro 
Cc: Oleg Nesterov 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc: Update get proc_pid_cmdline() to use mm.h helpers

2014-03-20T14:10:26+00:00

Re-factor proc_pid_cmdline() to use get_cmdline() helper
from mm.h.

Acked-by: David Rientjes 
Acked-by: Stephen Smalley 
Acked-by: Richard Guy Briggs 

Signed-off-by: William Roberts 
Acked-by: Richard Guy Briggs 
Signed-off-by: Eric Paris

fs/proc/base.c: fix GPF in /proc/$PID/map_files

2014-03-11T00:26:20+00:00

The expected logic of proc_map_files_get_link() is either to return 0
and initialize 'path' or return an error and leave 'path' uninitialized.

By the time dname_to_vma_addr() returns 0 the corresponding vma may have
already be gone.  In this case the path is not initialized but the
return value is still 0.  This results in 'general protection fault'
inside d_path().

Steps to reproduce:

  CONFIG_CHECKPOINT_RESTORE=y

    fd = open(...);
    while (1) {
        mmap(fd, ...);
        munmap(fd, ...);
    }

  ls -la /proc/$PID/map_files

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=68991

Signed-off-by: Artem Fetishev 
Signed-off-by: Aleksandr Terekhov 
Reported-by: 
Acked-by: Pavel Emelyanov 
Acked-by: Cyrill Gorcunov 
Reviewed-by: "Eric W. Biederman" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc: fix ->f_pos overflows in first_tid()

2014-01-24T00:37:01+00:00

1. proc_task_readdir()->first_tid() path truncates f_pos to int, this
   is wrong even on 64bit.

   We could check that f_pos < PID_MAX or even INT_MAX in
   proc_task_readdir(), but this patch simply checks the potential
   overflow in first_tid(), this check is nop on 64bit.  We do not care if
   it was negative and the new unsigned value is huge, all we need to
   ensure is that we never wrongly return !NULL.

2. Remove the 2nd "nr != 0" check before get_nr_threads(),
   nr_threads == 0 is not distinguishable from !pid_task() above.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: Michal Hocko 
Cc: Sameer Nanda 
Cc: Sergey Dyasly 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

proc: don't (ab)use ->group_leader in proc_task_readdir() paths

2014-01-24T00:37:01+00:00

proc_task_readdir() does not really need "leader", first_tid() has to
revalidate it anyway.  Just pass proc_pid(inode) to first_tid() instead,
it can do pid_task(PIDTYPE_PID) itself and read ->group_leader only if
necessary.

The patch also extracts the "inode is dead" code from
pid_delete_dentry(dentry) into the new trivial helper,
proc_inode_is_dead(inode), proc_task_readdir() uses it to return -ENOENT
if this dir was removed.

This is a bit racy, but the race is very inlikely and the getdents() after
openndir() can see the empty "." + ".." dir only once.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: Michal Hocko 
Cc: Sameer Nanda 
Cc: Sergey Dyasly 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds