[kernel-hardening] [PATCH v2 0/3] kallsyms: don't leak address

["Tobin C. Harding" <me@tobin.cc>]

This set plugs a kernel address leak that occurs if kallsyms symbol
look up fails. This set was prompted by a leaking address found using
scripts/leaking_addresses.pl on a PowerPC machine in the wild.

$ perl scripts/leaking_addresses.pl		[address sanitized]
...
/proc/8025/task/8025/stack: [<0000000000000000>] 0xc0000001XXXXXXXX

$ uname -r
4.4.0-79-powerpc64-smp


Patch set does not change behaviour when KALLSYMS is not defined
(suggested by Linus).

Comments on version 1 indicated that current behaviour may be useful for
debugging. This version adds a kernel command-line parameter in order to
be able to preserve current behaviour (print raw address if kallsyms
symbol look up fails). (Command-line parameter suggested by Steve.)

New command-line parameter is documented only in the kernel-doc for
kallsyms functions sprint_symbol() and sprint_symbol_no_offset(). Is
this sufficient? Perhaps an entry in printk-formats.txt also?

Patch 1 - return error code if symbol look up fails unless new
	  command-line parameter 'insecure_print_all_symbols' is enabled.
Patch 2 - print <symbol not found> to buffer if symbol look up returns
	  an error.
Patch 3 - maintain current behaviour in ftrace.

thanks,
Tobin.

v2:
 - Add kernel command-line parameter.
 - Remove unnecessary function.
 - Fix broken ftrace code (and actually build and test ftrace code).

Patch 1 and 2 tested. Patch 3 (ftrace) tested but not all code paths
executed (discussed with Steve in another thread).

Tobin C. Harding (3):
  kallsyms: don't leak address when symbol not found
  vsprintf: print <no-symbol> if symbol not found
  trace: print address if symbol not found

 kernel/kallsyms.c                | 31 +++++++++++++++++++++++++------
 kernel/trace/trace.h             | 24 ++++++++++++++++++++++++
 kernel/trace/trace_events_hist.c |  6 +++---
 kernel/trace/trace_output.c      |  2 +-
 lib/vsprintf.c                   | 11 ++++++++---
 5 files changed, 61 insertions(+), 13 deletions(-)

-- 
2.7.4