28 Jul, 2016
1 commit
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Several build configurations had already disabled this warning because
it generates a lot of false positives. But some had not, and it was
still enabled for "allmodconfig" builds, for example.Looking at the warnings produced, every single one I looked at was a
false positive, and the warnings are frequent enough (and big enough)
that they can easily hide real problems that you don't notice in the
noise generated by -Wmaybe-uninitialized.The warning is good in theory, but this is a classic case of a warning
that causes more problems than the warning can solve.If gcc gets better at avoiding false positives, we may be able to
re-enable this warning. But as is, we're better off without it, and I
want to be able to see the *real* warnings.Signed-off-by: Linus Torvalds
23 Mar, 2016
1 commit
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-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:* Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
such warnings for instrumented files.* Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
the all[yes|mod]config build goes without -fsanitize=* and still with
-Wmaybe-uninitialized.Signed-off-by: Andrey Ryabinin
Reported-by: Fengguang Wu
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Jan, 2016
1 commit
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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