UBSAN uses compile-time instrumentation to catch undefined behavior
(UB). Compiler inserts code that perform certain kinds of checks before
operations that could cause UB. If check fails (i.e. UB detected)
__ubsan_handle_* function called to print error message.
So the most of the work is done by compiler. This patch just implements
ubsan handlers printing errors.
GCC has this capability since 4.9.x [1] (see -fsanitize=undefined
option and its suboptions).
However GCC 5.x has more checkers implemented [2].
Article [3] has a bit more details about UBSAN in the GCC.
[1] - https://gcc.gnu.org/onlinedocs/gcc-4.9.0/gcc/Debugging-Options.html
[2] - https://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
[3] - http://developerblog.redhat.com/2014/10/16/gcc-undefined-behavior-sanitizer-ubsan/
Issues which UBSAN has found thus far are:
Found bugs:
* out-of-bounds access - 97840cb67ff5 ("netfilter: nfnetlink: fix
insufficient validation in nfnetlink_bind")
undefined shifts:
* d48458d4a768 ("jbd2: use a better hash function for the revoke
table")
* 10632008b9e1 ("clockevents: Prevent shift out of bounds")
* 'x << -1' shift in ext4 -
http://lkml.kernel.org/r/
* undefined rol32(0) -
http://lkml.kernel.org/r/
* undefined dirty_ratelimit calculation -
http://lkml.kernel.org/r/
* undefined roundown_pow_of_two(0) -
http://lkml.kernel.org/r/
* [WONTFIX] undefined shift in __bpf_prog_run -
http://lkml.kernel.org/r/
WONTFIX here because it should be fixed in bpf program, not in kernel.
signed overflows:
* 32a8df4e0b33f ("sched: Fix odd values in effective_load()
calculations")
* mul overflow in ntp -
http://lkml.kernel.org/r/
* incorrect conversion into rtc_time in rtc_time64_to_tm() -
http://lkml.kernel.org/r/
* unvalidated timespec in io_getevents() -
http://lkml.kernel.org/r/
* [NOTABUG] signed overflow in ktime_add_safe() -
http://lkml.kernel.org/r/
[akpm@linux-foundation.org: fix unused local warning]
[akpm@linux-foundation.org: fix __int128 build woes]
Signed-off-by: Andrey Ryabinin
Cc: Peter Zijlstra
Cc: Sasha Levin
Cc: Randy Dunlap
Cc: Rasmus Villemoes
Cc: Jonathan Corbet
Cc: Michal Marek
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: "H. Peter Anvin"
Cc: Yury Gribov
Cc: Dmitry Vyukov
Cc: Konstantin Khlebnikov
Cc: Kostya Serebryany
Cc: Johannes Berg
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds