linux.git/kernel/debug/kdb/kdb_main.c, branch v6.6.132

kdb: Fix a potential buffer overflow in kdb_local()

2024-01-25T23:36:00+00:00

[ Upstream commit 4f41d30cd6dc865c3cbc1a852372321eba6d4e4c ]

When appending "[defcmd]" to 'kdb_prompt_str', the size of the string
already in the buffer should be taken into account.

An option could be to switch from strncat() to strlcat() which does the
correct test to avoid such an overflow.

However, this actually looks as dead code, because 'defcmd_in_progress'
can't be true here.
See a more detailed explanation at [1].

[1]: https://lore.kernel.org/all/CAD=FV=WSh7wKN7Yp-3wWiDgX4E3isQ8uh0LCzTmd1v9Cg9j+nQ@mail.gmail.com/

Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Signed-off-by: Christophe JAILLET 
Reviewed-by: Douglas Anderson 
Signed-off-by: Sasha Levin

Merge tag 'modules-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux

2022-05-27T00:13:43+00:00

Pull modules updates from  Luis Chamberlain:

 - It was time to tidy up kernel/module.c and one way of starting with
   that effort was to split it up into files. At my request Aaron Tomlin
   spearheaded that effort with the goal to not introduce any functional
   at all during that endeavour. The penalty for the split is +1322
   bytes total, +112 bytes in data, +1210 bytes in text while bss is
   unchanged. One of the benefits of this other than helping make the
   code easier to read and review is summoning more help on review for
   changes with livepatching so kernel/module/livepatch.c is now pegged
   as maintained by the live patching folks.

   The before and after with just the move on a defconfig on x86-64:

     $ size kernel/module.o
        text    data     bss     dec     hex filename
       38434    4540     104   43078    a846 kernel/module.o

     $ size -t kernel/module/*.o
        text    data     bss     dec     hex filename
       4785     120       0    4905    1329 kernel/module/kallsyms.o
      28577    4416     104   33097    8149 kernel/module/main.o
       1158       8       0    1166     48e kernel/module/procfs.o
        902     108       0    1010     3f2 kernel/module/strict_rwx.o
       3390       0       0    3390     d3e kernel/module/sysfs.o
        832       0       0     832     340 kernel/module/tree_lookup.o
      39644    4652     104   44400    ad70 (TOTALS)

 - Aaron added module unload taint tracking (MODULE_UNLOAD_TAINT_TRACKING),
   to enable tracking unloaded modules which did taint the kernel.

 - Christophe Leroy added CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
   which lets architectures to request having modules data in vmalloc
   area instead of module area. There are three reasons why an
   architecture might want this:

    a) On some architectures (like book3s/32) it is not possible to
       protect against execution on a page basis. The exec stuff can be
       mapped by different arch segment sizes (on book3s/32 that is 256M
       segments). By default the module area is in an Exec segment while
       vmalloc area is in a NoExec segment. Using vmalloc lets you muck
       with module data as NoExec on those architectures whereas before
       you could not.

    b) By pushing more module data to vmalloc you also increase the
       probability of module text to remain within a closer distance
       from kernel core text and this reduces trampolines, this has been
       reported on arm first and powerpc folks are following that lead.

    c) Free'ing module_alloc() (Exec by default) area leaves this
       exposed as Exec by default, some architectures have some security
       enhancements to set this as NoExec on free, and splitting module
       data with text let's future generic special allocators be added
       to the kernel without having developers try to grok the tribal
       knowledge per arch. Work like Rick Edgecombe's permission vmalloc
       interface [0] becomes easier to address over time.

       [0] https://lore.kernel.org/lkml/20201120202426.18009-1-rick.p.edgecombe@intel.com/#r

 - Masahiro Yamada's symbol search enhancements

* tag 'modules-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: (33 commits)
  module: merge check_exported_symbol() into find_exported_symbol_in_section()
  module: do not binary-search in __ksymtab_gpl if fsa->gplok is false
  module: do not pass opaque pointer for symbol search
  module: show disallowed symbol name for inherit_taint()
  module: fix [e_shstrndx].sh_size=0 OOB access
  module: Introduce module unload taint tracking
  module: Move module_assert_mutex_or_preempt() to internal.h
  module: Make module_flags_taint() accept a module's taints bitmap and usable outside core code
  module.h: simplify MODULE_IMPORT_NS
  powerpc: Select ARCH_WANTS_MODULES_DATA_IN_VMALLOC on book3s/32 and 8xx
  module: Remove module_addr_min and module_addr_max
  module: Add CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC
  module: Introduce data_layout
  module: Prepare for handling several RB trees
  module: Always have struct mod_tree_root
  module: Rename debug_align() as strict_align()
  module: Rework layout alignment to avoid BUG_ON()s
  module: Move module_enable_x() and frob_text() in strict_rwx.c
  module: Make module_enable_x() independent of CONFIG_ARCH_HAS_STRICT_MODULE_RWX
  module: Move version support into a separate file
  ...

lockdown: also lock down previous kgdb use

2022-05-24T18:29:34+00:00

KGDB and KDB allow read and write access to kernel memory, and thus
should be restricted during lockdown.  An attacker with access to a
serial port (for example, via a hypervisor console, which some cloud
vendors provide over the network) could trigger the debugger so it is
important that the debugger respect the lockdown mode when/if it is
triggered.

Fix this by integrating lockdown into kdb's existing permissions
mechanism.  Unfortunately kgdb does not have any permissions mechanism
(although it certainly could be added later) so, for now, kgdb is simply
and brutally disabled by immediately exiting the gdb stub without taking
any action.

For lockdowns established early in the boot (e.g. the normal case) then
this should be fine but on systems where kgdb has set breakpoints before
the lockdown is enacted than "bad things" will happen.

CVE: CVE-2022-21499
Co-developed-by: Stephen Brennan 
Signed-off-by: Stephen Brennan 
Reviewed-by: Douglas Anderson 
Signed-off-by: Daniel Thompson 
Signed-off-by: Linus Torvalds

module: Move kdb module related code out of main kdb code

2022-04-05T15:43:04+00:00

No functional change.

This patch migrates the kdb 'lsmod' command support out of main
kdb code into its own file under kernel/module. In addition to
the above, a minor style warning i.e. missing a blank line after
declarations, was resolved too. The new file was added to
MAINTAINERS. Finally we remove linux/module.h as it is entirely
redundant.

Reviewed-by: Daniel Thompson 
Acked-by: Daniel Thompson 
Signed-off-by: Aaron Tomlin 
Signed-off-by: Luis Chamberlain

kdb: Adopt scheduler's task classification

2021-11-03T17:21:37+00:00

Currently kdb contains some open-coded routines to generate a summary
character for each task. This code currently issues warnings, is
almost certainly broken and won't make sense to any kernel dev who
has ever used /proc to examine task states.

Fix both the warning and the potential for confusion by adopting the
scheduler's task classification. Whilst doing this we also simplify the
filtering by using mask strings directly (which means we don't have to
guess all the characters the scheduler might give us).

Unfortunately we can't quite match the scheduler classification completely.
We add four extra states: - for idle loops and i, m and s for sleeping
system daemons (which means kthreads in one of the I, M and S states).
These extra states are used to manage the filters for tools to make the
output of ps and bta less noisy.

Note: The Fixes below is the last point the original dubious code was
      moved; it was not introduced by that patch. However it gives us
      the last point to which this patch can be easily backported.
      Happily that should be enough to cover the introduction of
      CONFIG_WERROR!

Fixes: 2f064a59a11f ("sched: Change task_struct::state")
Link: https://lore.kernel.org/r/20211102173158.3315227-1-daniel.thompson@linaro.org
Reviewed-by: Douglas Anderson 
Signed-off-by: Daniel Thompson

kdb: Rename members of struct kdbtab_t

2021-07-27T16:05:06+00:00

Remove redundant prefix "cmd_" from name of members in struct kdbtab_t
for better readibility.

Suggested-by: Doug Anderson 
Signed-off-by: Sumit Garg 
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20210712134620.276667-5-sumit.garg@linaro.org
Signed-off-by: Daniel Thompson

kdb: Simplify kdb_defcmd macro logic

2021-07-27T16:04:50+00:00

Switch to use a linked list instead of dynamic array which makes
allocation of kdb macro and traversing the kdb macro commands list
simpler.

Suggested-by: Daniel Thompson 
Signed-off-by: Sumit Garg 
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20210712134620.276667-4-sumit.garg@linaro.org
Signed-off-by: Daniel Thompson

kdb: Get rid of redundant kdb_register_flags()

2021-07-27T16:03:16+00:00

Commit e4f291b3f7bb ("kdb: Simplify kdb commands registration")
allowed registration of pre-allocated kdb commands with pointer to
struct kdbtab_t. Lets switch other users as well to register pre-
allocated kdb commands via:
- Changing prototype for kdb_register() to pass a pointer to struct
  kdbtab_t instead.
- Embed kdbtab_t structure in kdb_macro_t rather than individual params.

With these changes kdb_register_flags() becomes redundant and hence
removed. Also, since we have switched all users to register
pre-allocated commands, "is_dynamic" flag in struct kdbtab_t becomes
redundant and hence removed as well.

Suggested-by: Daniel Thompson 
Signed-off-by: Sumit Garg 
Acked-by: Steven Rostedt (VMware) 
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20210712134620.276667-3-sumit.garg@linaro.org
Signed-off-by: Daniel Thompson

kdb: Rename struct defcmd_set to struct kdb_macro

2021-07-27T16:00:14+00:00

Rename struct defcmd_set to struct kdb_macro as that sounds more
appropriate given its purpose.

Suggested-by: Daniel Thompson 
Signed-off-by: Sumit Garg 
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20210712134620.276667-2-sumit.garg@linaro.org
Signed-off-by: Daniel Thompson

Merge tag 'kgdb-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux

2021-07-06T18:29:18+00:00

Pull kgdb updates from Daniel Thompson:
 "This was a extremely quiet cycle for kgdb. This consists of two
  patches that between them address spelling errors and a switch
  fallthrough warning"

* tag 'kgdb-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux:
  kgdb: Fix fall-through warning for Clang
  kgdb: Fix spelling mistakes