linux.git/drivers/misc/lkdtm, branch master

refcount: Report UAF for refcount_sub_and_test(0) when counter==0

2024-08-05T21:34:23+00:00

When a reference counter is at zero and refcount_sub_and_test() is invoked
to subtract zero, the function accepts this request without any warning and
returns true. This behavior does not seem ideal because the counter being
already at zero indicates a use-after-free. Furthermore, returning true by
refcount_sub_and_test() in this case potentially results in a double-free
done by its caller.

Modify the underlying function __refcount_sub_and_test() to warn about this
case as a use-after-free and have it return false to avoid the potential
double-free.

Signed-off-by: Petr Pavlu 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20240717130023.5675-1-petr.pavlu@suse.com
Signed-off-by: Kees Cook

lkdtm/bugs: add test for hung smp_call_function_single()

2024-06-17T18:17:31+00:00

The CONFIG_CSD_LOCK_WAIT_DEBUG option enables debugging of hung
smp_call_function*() calls (e.g. when the target CPU gets stuck within
the callback function). Testing this option requires triggering such
hangs.

This patch adds an lkdtm test with a hung smp_call_function_single()
callback, which can be used to test CONFIG_CSD_LOCK_WAIT_DEBUG and NMI
backtraces (as CONFIG_CSD_LOCK_WAIT_DEBUG will attempt an NMI backtrace
of the hung target CPU).

On arm64 using pseudo-NMI, this looks like:

| # mount -t debugfs none /sys/kernel/debug/
| # echo SMP_CALL_LOCKUP > /sys/kernel/debug/provoke-crash/DIRECT
| lkdtm: Performing direct entry SMP_CALL_LOCKUP
| smp: csd: Detected non-responsive CSD lock (#1) on CPU#1, waiting 5000000176 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp:     csd: CSD lock (#1) handling this request.
| Sending NMI from CPU 1 to CPUs 0:
| NMI backtrace for cpu 0
| CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.9.0-rc4-00001-gfdfd281212ec #1
| Hardware name: linux,dummy-virt (DT)
| pstate: 60401005 (nZCv daif +PAN -UAO -TCO -DIT +SSBS BTYPE=--)
| pc : __lkdtm_SMP_CALL_LOCKUP+0x0/0x8
| lr : __flush_smp_call_function_queue+0x1b0/0x290
| sp : ffff800080003f30
| pmr_save: 00000060
| x29: ffff800080003f30 x28: ffffa4ce961a4900 x27: 0000000000000000
| x26: fff000003fcfa0c0 x25: ffffa4ce961a4900 x24: ffffa4ce959aa140
| x23: ffffa4ce959aa140 x22: 0000000000000000 x21: ffff800080523c40
| x20: 0000000000000000 x19: 0000000000000000 x18: fff05b31aa323000
| x17: fff05b31aa323000 x16: ffff800080000000 x15: 0000330fc3fe6b2c
| x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000279
| x11: 0000000000000040 x10: fff000000302d0a8 x9 : fff000000302d0a0
| x8 : fff0000003400270 x7 : 0000000000000000 x6 : ffffa4ce9451b810
| x5 : 0000000000000000 x4 : fff05b31aa323000 x3 : ffff800080003f30
| x2 : fff05b31aa323000 x1 : ffffa4ce959aa140 x0 : 0000000000000000
| Call trace:
|  __lkdtm_SMP_CALL_LOCKUP+0x0/0x8
|  generic_smp_call_function_single_interrupt+0x14/0x20
|  ipi_handler+0xb8/0x178
|  handle_percpu_devid_irq+0x84/0x130
|  generic_handle_domain_irq+0x2c/0x44
|  gic_handle_irq+0x118/0x240
|  call_on_irq_stack+0x24/0x4c
|  do_interrupt_handler+0x80/0x84
|  el1_interrupt+0x44/0xc0
|  el1h_64_irq_handler+0x18/0x24
|  el1h_64_irq+0x78/0x7c
|  default_idle_call+0x40/0x60
|  do_idle+0x23c/0x2d0
|  cpu_startup_entry+0x38/0x3c
|  kernel_init+0x0/0x1d8
|  start_kernel+0x51c/0x608
|  __primary_switched+0x80/0x88
| CPU: 1 PID: 128 Comm: sh Not tainted 6.9.0-rc4-00001-gfdfd281212ec #1
| Hardware name: linux,dummy-virt (DT)
| Call trace:
|  dump_backtrace+0x90/0xe8
|  show_stack+0x18/0x24
|  dump_stack_lvl+0xac/0xe8
|  dump_stack+0x18/0x24
|  csd_lock_wait_toolong+0x268/0x338
|  smp_call_function_single+0x1dc/0x2f0
|  lkdtm_SMP_CALL_LOCKUP+0xcc/0xfc
|  lkdtm_do_action+0x1c/0x38
|  direct_entry+0xbc/0x14c
|  full_proxy_write+0x60/0xb4
|  vfs_write+0xd0/0x35c
|  ksys_write+0x70/0x104
|  __arm64_sys_write+0x1c/0x28
|  invoke_syscall+0x48/0x114
|  el0_svc_common.constprop.0+0x40/0xe0
|  do_el0_svc+0x1c/0x28
|  el0_svc+0x38/0x108
|  el0t_64_sync_handler+0x120/0x12c
|  el0t_64_sync+0x1a4/0x1a8
| smp: csd: Continued non-responsive CSD lock (#1) on CPU#1, waiting 10000064272 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp:     csd: CSD lock (#1) handling this request.
| smp: csd: Continued non-responsive CSD lock (#1) on CPU#1, waiting 15000064384 ns for CPU#00 __lkdtm_SMP_CALL_LOCKUP+0x0/0x8(0x0).
| smp:     csd: CSD lock (#1) handling this request.

Signed-off-by: Mark Rutland 
Acked-by: Paul E. McKenney 
Cc: Kees Cook 
Link: https://lore.kernel.org/r/20240515120828.375585-1-mark.rutland@arm.com
Signed-off-by: Kees Cook

Merge tag 'kbuild-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

2024-05-18T19:39:20+00:00

Pull Kbuild updates from Masahiro Yamada:

 - Avoid 'constexpr', which is a keyword in C23

 - Allow 'dtbs_check' and 'dt_compatible_check' run independently of
   'dt_binding_check'

 - Fix weak references to avoid GOT entries in position-independent code
   generation

 - Convert the last use of 'optional' property in arch/sh/Kconfig

 - Remove support for the 'optional' property in Kconfig

 - Remove support for Clang's ThinLTO caching, which does not work with
   the .incbin directive

 - Change the semantics of $(src) so it always points to the source
   directory, which fixes Makefile inconsistencies between upstream and
   downstream

 - Fix 'make tar-pkg' for RISC-V to produce a consistent package

 - Provide reasonable default coverage for objtool, sanitizers, and
   profilers

 - Remove redundant OBJECT_FILES_NON_STANDARD, KASAN_SANITIZE, etc.

 - Remove the last use of tristate choice in drivers/rapidio/Kconfig

 - Various cleanups and fixes in Kconfig

* tag 'kbuild-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (46 commits)
  kconfig: use sym_get_choice_menu() in sym_check_prop()
  rapidio: remove choice for enumeration
  kconfig: lxdialog: remove initialization with A_NORMAL
  kconfig: m/nconf: merge two item_add_str() calls
  kconfig: m/nconf: remove dead code to display value of bool choice
  kconfig: m/nconf: remove dead code to display children of choice members
  kconfig: gconf: show checkbox for choice correctly
  kbuild: use GCOV_PROFILE and KCSAN_SANITIZE in scripts/Makefile.modfinal
  Makefile: remove redundant tool coverage variables
  kbuild: provide reasonable defaults for tool coverage
  modules: Drop the .export_symbol section from the final modules
  kconfig: use menu_list_for_each_sym() in sym_check_choice_deps()
  kconfig: use sym_get_choice_menu() in conf_write_defconfig()
  kconfig: add sym_get_choice_menu() helper
  kconfig: turn defaults and additional prompt for choice members into error
  kconfig: turn missing prompt for choice members into error
  kconfig: turn conf_choice() into void function
  kconfig: use linked list in sym_set_changed()
  kconfig: gconf: use MENU_CHANGED instead of SYMBOL_CHANGED
  kconfig: gconf: remove debug code
  ...

Makefile: remove redundant tool coverage variables

2024-05-14T14:35:48+00:00

Now Kbuild provides reasonable defaults for objtool, sanitizers, and
profilers.

Remove redundant variables.

Note:

This commit changes the coverage for some objects:

  - include arch/mips/vdso/vdso-image.o into UBSAN, GCOV, KCOV
  - include arch/sparc/vdso/vdso-image-*.o into UBSAN
  - include arch/sparc/vdso/vma.o into UBSAN
  - include arch/x86/entry/vdso/extable.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
  - include arch/x86/entry/vdso/vdso-image-*.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
  - include arch/x86/entry/vdso/vdso32-setup.o into KASAN, KCSAN, UBSAN, GCOV, KCOV
  - include arch/x86/entry/vdso/vma.o into GCOV, KCOV
  - include arch/x86/um/vdso/vma.o into KASAN, GCOV, KCOV

I believe these are positive effects because all of them are kernel
space objects.

Signed-off-by: Masahiro Yamada 
Reviewed-by: Kees Cook 
Tested-by: Roberto Sassu

lkdtm: Disable CFI checking for perms functions

2024-05-01T19:37:42+00:00

The EXEC_RODATA test plays a lot of tricks to live in the .rodata section,
and once again ran into objtool's (completely reasonable) assumptions
that executable code should live in an executable section. However, this
manifested only under CONFIG_CFI_CLANG=y, as one of the .cfi_sites was
pointing into the .rodata section.

Since we're testing non-CFI execution properties in perms.c (and
rodata.c), we can disable CFI for the involved functions, and remove the
CFI arguments from rodata.c entirely.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-lkp/202308301532.d7acf63e-oliver.sang@intel.com
Fixes: 6342a20efbd8 ("objtool: Add elf_create_section_pair()")
Link: https://lore.kernel.org/r/20240430234953.work.760-kees@kernel.org
Signed-off-by: Kees Cook

lkdtm/bugs: Improve warning message for compilers without counted_by support

2024-03-22T23:25:31+00:00

The current message for telling the user that their compiler does not
support the counted_by attribute in the FAM_BOUNDS test does not make
much sense either grammatically or semantically. Fix it to make it
correct in both aspects.

Signed-off-by: Nathan Chancellor 
Reviewed-by: Gustavo A. R. Silva 
Link: https://lore.kernel.org/r/20240321-lkdtm-improve-lack-of-counted_by-msg-v1-1-0fbf7481a29c@kernel.org
Signed-off-by: Kees Cook

Merge tag 'slab-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2024-03-13T03:14:54+00:00

Pull slab updates from Vlastimil Babka:

 - Freelist loading optimization (Chengming Zhou)

   When the per-cpu slab is depleted and a new one loaded from the cpu
   partial list, optimize the loading to avoid an irq enable/disable
   cycle. This results in a 3.5% performance improvement on the "perf
   bench sched messaging" test.

 - Kernel boot parameters cleanup after SLAB removal (Xiongwei Song)

   Due to two different main slab implementations we've had boot
   parameters prefixed either slab_ and slub_ with some later becoming
   an alias as both implementations gained the same functionality (i.e.
   slab_nomerge vs slub_nomerge). In order to eventually get rid of the
   implementation-specific names, the canonical and documented
   parameters are now all prefixed slab_ and the slub_ variants become
   deprecated but still working aliases.

 - SLAB_ kmem_cache creation flags cleanup (Vlastimil Babka)

   The flags had hardcoded #define values which became tedious and
   error-prone when adding new ones. Assign the values via an enum that
   takes care of providing unique bit numbers. Also deprecate
   SLAB_MEM_SPREAD which was only used by SLAB, so it's a no-op since
   SLAB removal. Assign it an explicit zero value. The removals of the
   flag usage are handled independently in the respective subsystems,
   with a final removal of any leftover usage planned for the next
   release.

 - Misc cleanups and fixes (Chengming Zhou, Xiaolei Wang, Zheng Yejian)

   Includes removal of unused code or function parameters and a fix of a
   memleak.

* tag 'slab-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab:
  slab: remove PARTIAL_NODE slab_state
  mm, slab: remove memcg_from_slab_obj()
  mm, slab: remove the corner case of inc_slabs_node()
  mm/slab: Fix a kmemleak in kmem_cache_destroy()
  mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE
  mm, slab: use an enum to define SLAB_ cache creation flags
  mm, slab: deprecate SLAB_MEM_SPREAD flag
  mm, slab: fix the comment of cpu partial list
  mm, slab: remove unused object_size parameter in kmem_cache_flags()
  mm/slub: remove parameter 'flags' in create_kmalloc_caches()
  mm/slub: remove unused parameter in next_freelist_entry()
  mm/slub: remove full list manipulation for non-debug slab
  mm/slub: directly load freelist from cpu partial slab in the likely case
  mm/slub: make the description of slab_min_objects helpful in doc
  mm/slub: replace slub_$params with slab_$params in slub.rst
  mm/slub: unify all sl[au]b parameters with "slab_$param"
  Documentation: kernel-parameters: remove noaliencache

lkdtm/bugs: In lkdtm_HUNG_TASK() use BUG(), not BUG_ON(1)

2024-02-01T17:44:07+00:00

In commit edb6538da3df ("lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid
tail call optimization") we marked lkdtm_HUNG_TASK() as
__noreturn. The compiler gets unhappy if it thinks a __noreturn
function might return, so there's a BUG_ON(1) at the end. Any human
can see that the function won't return and the compiler can figure
that out too. Except when it can't.

The MIPS architecture defines HAVE_ARCH_BUG_ON and defines its own
version of BUG_ON(). The MIPS version of BUG_ON() is not a macro but
is instead an inline function. Apparently this prevents the compiler
from realizing that the condition to BUG_ON() is constant and that the
function will never return.

Let's change the BUG_ON(1) to just BUG(), which it should have been to
begin with. The only reason I used BUG_ON(1) to begin with was because
I was used to using WARN_ON(1) when writing test code and WARN() and
BUG() are oddly inconsistent in this manner. :-/

Fixes: edb6538da3df ("lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid tail call optimization")
Signed-off-by: Douglas Anderson 
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-kbuild-all/202401262204.wUFKRYZF-lkp@intel.com/
Acked-by: Arnd Bergmann 
Link: https://lore.kernel.org/r/20240126072852.1.Ib065e528a8620474a72f15baa2feead1f3d89865@changeid
Signed-off-by: Kees Cook

lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid tail call optimization

2024-02-01T17:44:07+00:00

When testing with lkdtm_HUNG_TASK() and looking at the output, I
expected to see lkdtm_HUNG_TASK() in the stack crawl but it wasn't
there. Instead, the top function on at least some devices was
schedule() due to tail call optimization.

Let's do two things to help here:
1. We'll mark this as "__noreturn". On GCC at least this is documented
   to prevent tail call optimization. The docs [1] say "In order to
   preserve backtraces, GCC will never turn calls to noreturn
   functions into tail calls."
2. We'll add a BUG_ON(1) at the end which means that schedule() is no
   longer a tail call. Note that this is potentially important because
   if we _did_ end up returning from schedule() due to some weird
   issue then we'd potentially be violating the "noreturn" that we
   told the compiler about. BUG is the right thing to do here.

[1] https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html

Signed-off-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20240122164935.2.I26e8f68c312824fcc80c19d4e91de2d2bef958f0@changeid
Signed-off-by: Kees Cook

lkdtm: Make lkdtm_do_action() return to avoid tail call optimization

2024-02-01T17:44:07+00:00

The comments for lkdtm_do_action() explicitly call out that it
shouldn't be inlined because we want it to show up in stack
crawls. However, at least with some compilers / options it's still
vanishing due to tail call optimization. Let's add a return value to
the function to make it harder for the compiler to do tail call
optimization here.

Now that we have a return value, we can actually use it in the
callers, which is a minor improvement in the code.

Signed-off-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20240122164935.1.I345e485f36babad76370c59659a706723750d950@changeid
Signed-off-by: Kees Cook