linux-toradex.git/include/linux/signal.h, branch v5.1-rc4

signal: Make siginmask safe when passed a signal of 0

2019-01-12T17:48:20+00:00

Eric Biggers reported:
> The following commit, which went into v4.20, introduced undefined behavior when
> sys_rt_sigqueueinfo() is called with sig=0:
>
> commit 4ce5f9c9e7546915c559ffae594e6d73f918db00
> Author: Eric W. Biederman 
> Date:   Tue Sep 25 12:59:31 2018 +0200
>
>     signal: Use a smaller struct siginfo in the kernel
>
> In sig_specific_sicodes(), used from known_siginfo_layout(), the expression
> '1ULL << ((sig)-1)' is undefined as it evaluates to 1ULL << 4294967295.
>
> Reproducer:
>
> #include 
> #include 
> #include 
>
> int main(void)
> {
> 	siginfo_t si = { .si_code = 1 };
> 	syscall(__NR_rt_sigqueueinfo, 0, 0, &si);
> }
>
> UBSAN report for v5.0-rc1:
>
> UBSAN: Undefined behaviour in kernel/signal.c:2946:7
> shift exponent 4294967295 is too large for 64-bit type 'long unsigned int'
> CPU: 2 PID: 346 Comm: syz_signal Not tainted 5.0.0-rc1 #25
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x70/0xa5 lib/dump_stack.c:113
>  ubsan_epilogue+0xd/0x40 lib/ubsan.c:159
>  __ubsan_handle_shift_out_of_bounds+0x12c/0x170 lib/ubsan.c:425
>  known_siginfo_layout+0xae/0xe0 kernel/signal.c:2946
>  post_copy_siginfo_from_user kernel/signal.c:3009 [inline]
>  __copy_siginfo_from_user+0x35/0x60 kernel/signal.c:3035
>  __do_sys_rt_sigqueueinfo kernel/signal.c:3553 [inline]
>  __se_sys_rt_sigqueueinfo kernel/signal.c:3549 [inline]
>  __x64_sys_rt_sigqueueinfo+0x31/0x70 kernel/signal.c:3549
>  do_syscall_64+0x4c/0x1b0 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x433639
> Code: c4 18 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 27 00 00 c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fffcb289fc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000081
> RAX: ffffffffffffffda RBX: 00000000004002e0 RCX: 0000000000433639
> RDX: 00007fffcb289fd0 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 00000000006b2018 R08: 000000000000004d R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401560
> R13: 00000000004015f0 R14: 0000000000000000 R15: 0000000000000000

I have looked at the other callers of siginmask and they all appear to
in locations where sig can not be zero.

I have looked at the code generation of adding an extra test against
zero and gcc was able with a simple decrement instruction to combine
the two tests together. So the at most adding this test cost a single
cpu cycle.  In practice that decrement instruction was already present
as part of the mask comparison, so the only change was when the
instruction was executed.

So given that it is cheap, and obviously correct to update siginmask
to verify the signal is not zero.  Fix this issue there to avoid any
future problems.

Reported-by: Eric Biggers 
Fixes: 4ce5f9c9e754 ("signal: Use a smaller struct siginfo in the kernel")
Signed-off-by: "Eric W. Biederman"

signal: Add restore_user_sigmask()

2018-12-06T16:22:53+00:00

Refactor the logic to restore the sigmask before the syscall
returns into an api.
This is useful for versions of syscalls that pass in the
sigmask and expect the current->sigmask to be changed during
the execution and restored after the execution of the syscall.

With the advent of new y2038 syscalls in the subsequent patches,
we add two more new versions of the syscalls (for pselect, ppoll
and io_pgetevents) in addition to the existing native and compat
versions. Adding such an api reduces the logic that would need to
be replicated otherwise.

Signed-off-by: Deepa Dinamani 
Signed-off-by: Arnd Bergmann

signal: Add set_user_sigmask()

2018-12-06T16:22:38+00:00

Refactor reading sigset from userspace and updating sigmask
into an api.

This is useful for versions of syscalls that pass in the
sigmask and expect the current->sigmask to be changed during,
and restored after, the execution of the syscall.

With the advent of new y2038 syscalls in the subsequent patches,
we add two more new versions of the syscalls (for pselect, ppoll,
and io_pgetevents) in addition to the existing native and compat
versions. Adding such an api reduces the logic that would need to
be replicated otherwise.

Note that the calls to sigprocmask() ignored the return value
from the api as the function only returns an error on an invalid
first argument that is hardcoded at these call sites.
The updated logic uses set_current_blocked() instead.

Signed-off-by: Deepa Dinamani 
Signed-off-by: Arnd Bergmann

include/linux/signal.h: mark expected switch fall-throughs

2018-10-31T15:54:14+00:00

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where
we are expecting to fall through.

Link: http://lkml.kernel.org/r/20181013114847.GA3160@embeddedor.com
Signed-off-by: Gustavo A. R. Silva 
Acked-by: Kees Cook 
Reviewed-by: Michael Ellerman 
Cc: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

signal: Guard against negative signal numbers in copy_siginfo_from_user32

2018-10-11T01:34:14+00:00

While fixing an out of bounds array access in known_siginfo_layout
reported by the kernel test robot it became apparent that the same bug
exists in siginfo_layout and affects copy_siginfo_from_user32.

The straight forward fix that makes guards against making this mistake
in the future and should keep the code size small is to just take an
unsigned signal number instead of a signed signal number, as I did to
fix known_siginfo_layout.

Cc: stable@vger.kernel.org
Fixes: cc731525f26a ("signal: Remove kernel interal si_code magic")
Signed-off-by: "Eric W. Biederman"

signal: Use a smaller struct siginfo in the kernel

2018-10-03T14:50:39+00:00

We reserve 128 bytes for struct siginfo but only use about 48 bytes on
64bit and 32 bytes on 32bit.  Someday we might use more but it is unlikely
to be anytime soon.

Userspace seems content with just enough bytes of siginfo to implement
sigqueue.  Or in the case of checkpoint/restart reinjecting signals
the kernel has sent.

Reducing the stack footprint and the work to copy siginfo around from
2 cachelines to 1 cachelines seems worth doing even if I don't have
benchmarks to show a performance difference.

Suggested-by: Linus Torvalds 
Signed-off-by: "Eric W. Biederman"

signal: Distinguish between kernel_siginfo and siginfo

2018-10-03T14:47:43+00:00

Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo.  Keeping the
traditional name for the userspace definition.  While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo.  The reduction in size comes in a following change.

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

signal: Introduce copy_siginfo_from_user and use it's return value

2018-10-03T14:47:15+00:00

In preparation for using a smaller version of siginfo in the kernel
introduce copy_siginfo_from_user and use it when siginfo is copied from
userspace.

Make the pattern for using copy_siginfo_from_user and
copy_siginfo_from_user32 to capture the return value and return that
value on error.

This is a necessary prerequisite for using a smaller siginfo
in the kernel than the kernel exports to userspace.

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

Merge branch 'akpm' (patches from Andrew)

2018-08-22T19:34:08+00:00

Merge more updates from Andrew Morton:

 - the rest of MM

 - procfs updates

 - various misc things

 - more y2038 fixes

 - get_maintainer updates

 - lib/ updates

 - checkpatch updates

 - various epoll updates

 - autofs updates

 - hfsplus

 - some reiserfs work

 - fatfs updates

 - signal.c cleanups

 - ipc/ updates

* emailed patches from Andrew Morton : (166 commits)
  ipc/util.c: update return value of ipc_getref from int to bool
  ipc/util.c: further variable name cleanups
  ipc: simplify ipc initialization
  ipc: get rid of ids->tables_initialized hack
  lib/rhashtable: guarantee initial hashtable allocation
  lib/rhashtable: simplify bucket_table_alloc()
  ipc: drop ipc_lock()
  ipc/util.c: correct comment in ipc_obtain_object_check
  ipc: rename ipcctl_pre_down_nolock()
  ipc/util.c: use ipc_rcu_putref() for failues in ipc_addid()
  ipc: reorganize initialization of kern_ipc_perm.seq
  ipc: compute kern_ipc_perm.id under the ipc lock
  init/Kconfig: remove EXPERT from CHECKPOINT_RESTORE
  fs/sysv/inode.c: use ktime_get_real_seconds() for superblock stamp
  adfs: use timespec64 for time conversion
  kernel/sysctl.c: fix typos in comments
  drivers/rapidio/devices/rio_mport_cdev.c: remove redundant pointer md
  fork: don't copy inconsistent signal handler state to child
  signal: make get_signal() return bool
  signal: make sigkill_pending() return bool
  ...

signal: make get_signal() return bool

2018-08-22T17:52:51+00:00

make get_signal() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-18-christian@brauner.io
Signed-off-by: Christian Brauner 
Reviewed-by: Andrew Morton 
Cc: Al Viro 
Cc: Eric W. Biederman 
Cc: Greg Kroah-Hartman 
Cc: Ingo Molnar 
Cc: James Morris 
Cc: Kees Cook 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Stephen Smalley 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds