linux-stable.git/include/linux/sched.h, branch v4.4.263

futex: Add mutex around futex exit

2021-02-03T22:16:16+00:00

commit 3f186d974826847a07bc7964d79ec4eded475ad9 upstream.

The mutex will be used in subsequent changes to replace the busy looping of
a waiter when the futex owner is currently executing the exit cleanup to
prevent a potential live lock.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20191106224556.845798895@linutronix.de
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Lee Jones 
Signed-off-by: Greg Kroah-Hartman

exit/exec: Seperate mm_release()

2021-02-03T22:16:16+00:00

commit 4610ba7ad877fafc0a25a30c6c82015304120426 upstream.

mm_release() contains the futex exit handling. mm_release() is called from
do_exit()->exit_mm() and from exec()->exec_mm().

In the exit_mm() case PF_EXITING and the futex state is updated. In the
exec_mm() case these states are not touched.

As the futex exit code needs further protections against exit races, this
needs to be split into two functions.

Preparatory only, no functional change.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20191106224556.240518241@linutronix.de
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Lee Jones 
Signed-off-by: Greg Kroah-Hartman

futex: Replace PF_EXITPIDONE with a state

2021-02-03T22:16:16+00:00

commit 3d4775df0a89240f671861c6ab6e8d59af8e9e41 upstream.

The futex exit handling relies on PF_ flags. That's suboptimal as it
requires a smp_mb() and an ugly lock/unlock of the exiting tasks pi_lock in
the middle of do_exit() to enforce the observability of PF_EXITING in the
futex code.

Add a futex_state member to task_struct and convert the PF_EXITPIDONE logic
over to the new state. The PF_EXITING dependency will be cleaned up in a
later step.

This prepares for handling various futex exit issues later.

Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20191106224556.149449274@linutronix.de
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Lee Jones 
Signed-off-by: Greg Kroah-Hartman

signal: Extend exec_id to 64bits

2020-04-24T05:57:12+00:00

commit d1e7fd6462ca9fc76650fbe6ca800e35b24267da upstream.

Replace the 32bit exec_id with a 64bit exec_id to make it impossible
to wrap the exec_id counter.  With care an attacker can cause exec_id
wrap and send arbitrary signals to a newly exec'd parent.  This
bypasses the signal sending checks if the parent changes their
credentials during exec.

The severity of this problem can been seen that in my limited testing
of a 32bit exec_id it can take as little as 19s to exec 65536 times.
Which means that it can take as little as 14 days to wrap a 32bit
exec_id.  Adam Zabrocki has succeeded wrapping the self_exe_id in 7
days.  Even my slower timing is in the uptime of a typical server.
Which means self_exec_id is simply a speed bump today, and if exec
gets noticably faster self_exec_id won't even be a speed bump.

Extending self_exec_id to 64bits introduces a problem on 32bit
architectures where reading self_exec_id is no longer atomic and can
take two read instructions.  Which means that is is possible to hit
a window where the read value of exec_id does not match the written
value.  So with very lucky timing after this change this still
remains expoiltable.

I have updated the update of exec_id on exec to use WRITE_ONCE
and the read of exec_id in do_notify_parent to use READ_ONCE
to make it clear that there is no locking between these two
locations.

Link: https://lore.kernel.org/kernel-hardening/20200324215049.GA3710@pi3.com.pl
Fixes: 2.3.23pre2
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

sched/core: Add try_get_task_stack() and put_task_stack()

2019-12-21T09:35:04+00:00

commit c6c314a613cd7d03fb97713e0d642b493de42e69 upstream.

There are a few places in the kernel that access stack memory
belonging to a different task.  Before we can start freeing task
stacks before the task_struct is freed, we need a way for those code
paths to pin the stack.

Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Jann Horn 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/17a434f50ad3d77000104f21666575e10a9c1fbd.1474003868.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: zhangyi (F) 
Signed-off-by: Greg Kroah-Hartman

sched/core: Allow putting thread_info into task_struct

2019-12-21T09:35:04+00:00

commit c65eacbe290b8141554c71b2c94489e73ade8c8d upstream.

If an arch opts in by setting CONFIG_THREAD_INFO_IN_TASK_STRUCT,
then thread_info is defined as a single 'u32 flags' and is the first
entry of task_struct.  thread_info::task is removed (it serves no
purpose if thread_info is embedded in task_struct), and
thread_info::cpu gets its own slot in task_struct.

This is heavily based on a patch written by Linus.

Originally-from: Linus Torvalds 
Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Jann Horn 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/a0898196f0476195ca02713691a5037a14f2aac5.1473801993.git.luto@kernel.org
Signed-off-by: Ingo Molnar 
Signed-off-by: zhangyi (F) 
Signed-off-by: Greg Kroah-Hartman

sched/fair: Don't free p->numa_faults with concurrent readers

2019-08-04T07:35:02+00:00

commit 16d51a590a8ce3befb1308e0e7ab77f3b661af33 upstream.

When going through execve(), zero out the NUMA fault statistics instead of
freeing them.

During execve, the task is reachable through procfs and the scheduler. A
concurrent /proc/*/sched reader can read data from a freed ->numa_faults
allocation (confirmed by KASAN) and write it back to userspace.
I believe that it would also be possible for a use-after-free read to occur
through a race between a NUMA fault and execve(): task_numa_fault() can
lead to task_numa_compare(), which invokes task_weight() on the currently
running task of a different CPU.

Another way to fix this would be to make ->numa_faults RCU-managed or add
extra locking, but it seems easier to wipe the NUMA fault statistics on
execve.

Signed-off-by: Jann Horn 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Sergey Senozhatsky 
Cc: Thomas Gleixner 
Cc: Will Deacon 
Fixes: 82727018b0d3 ("sched/numa: Call task_numa_free() from do_execve()")
Link: https://lkml.kernel.org/r/20190716152047.14424-1-jannh@google.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

userfaultfd: don't pin the user memory in userfaultfd_file_create()

2019-06-11T10:24:11+00:00

commit d2005e3f41d4f9299e2df6a967c8beb5086967a9 upstream.

userfaultfd_file_create() increments mm->mm_users; this means that the
memory won't be unmapped/freed if mm owner exits/execs, and UFFDIO_COPY
after that can populate the orphaned mm more.

Change userfaultfd_file_create() and userfaultfd_ctx_put() to use
mm->mm_count to pin mm_struct.  This means that
atomic_inc_not_zero(mm->mm_users) is needed when we are going to
actually play with this memory.  Except handle_userfault() path doesn't
need this, the caller must already have a reference.

The patch adds the new trivial helper, mmget_not_zero(), it can have
more users.

Link: http://lkml.kernel.org/r/20160516172254.GA8595@redhat.com
Signed-off-by: Oleg Nesterov 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add prctl() control for indirect branch speculation

2019-05-16T17:45:12+00:00

commit 9137bb27e60e554dab694eafa4cca241fa3a694f upstream.

Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and
PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of
indirect branch speculation via STIBP and IBPB.

Invocations:
 Check indirect branch speculation status with
 - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0);

 Enable indirect branch speculation with
 - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0);

 Disable indirect branch speculation with
 - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0);

 Force disable indirect branch speculation with
 - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0);

See Documentation/userspace-api/spec_ctrl.rst.

Signed-off-by: Tim Chen 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Andy Lutomirski 
Cc: Linus Torvalds 
Cc: Jiri Kosina 
Cc: Tom Lendacky 
Cc: Josh Poimboeuf 
Cc: Andrea Arcangeli 
Cc: David Woodhouse 
Cc: Andi Kleen 
Cc: Dave Hansen 
Cc: Casey Schaufler 
Cc: Asit Mallick 
Cc: Arjan van de Ven 
Cc: Jon Masters 
Cc: Waiman Long 
Cc: Greg KH 
Cc: Dave Stewart 
Cc: Kees Cook 
Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de
[bwh: Backported to 4.4:
 - Renumber the PFA flags
 - Drop changes in tools/include/uapi/linux/prctl.h
 - Adjust filename]
Signed-off-by: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman

exec: avoid gcc-8 warning for get_task_comm

2018-12-13T08:21:28+00:00

commit 3756f6401c302617c5e091081ca4d26ab604bec5 upstream.

gcc-8 warns about using strncpy() with the source size as the limit:

  fs/exec.c:1223:32: error: argument to 'sizeof' in 'strncpy' call is the same expression as the source; did you mean to use the size of the destination? [-Werror=sizeof-pointer-memaccess]

This is indeed slightly suspicious, as it protects us from source
arguments without NUL-termination, but does not guarantee that the
destination is terminated.

This keeps the strncpy() to ensure we have properly padded target
buffer, but ensures that we use the correct length, by passing the
actual length of the destination buffer as well as adding a build-time
check to ensure it is exactly TASK_COMM_LEN.

There are only 23 callsites which I all reviewed to ensure this is
currently the case.  We could get away with doing only the check or
passing the right length, but it doesn't hurt to do both.

Link: http://lkml.kernel.org/r/20171205151724.1764896-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann 
Suggested-by: Kees Cook 
Acked-by: Kees Cook 
Acked-by: Ingo Molnar 
Cc: Alexander Viro 
Cc: Peter Zijlstra 
Cc: Serge Hallyn 
Cc: James Morris 
Cc: Aleksa Sarai 
Cc: "Eric W. Biederman" 
Cc: Frederic Weisbecker 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman