Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH 1/3] Fix backward-ring-buffer.c format-truncation error | Date | Thu, 25 Jul 2019 13:08:45 +0000 |
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From: Numfor Mbiziwo-Tiapo > Sent: 24 July 2019 19:45 > > Perf does not build with the ubsan (undefined behavior sanitizer) > and there is an error that says: > > tests/backward-ring-buffer.c:23:45: error: ‘%d’ directive output > may be truncated writing between 1 and 10 bytes into a region of > size 8 [-Werror=format-truncation=] > snprintf(proc_name, sizeof(proc_name), "p:%d\n", i); > > This can be reproduced by running (from the tip directory): > make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined" > > Th error occurs because they are writing to the 10 byte buffer - the > index 'i' of the for loop and the 2 byte hardcoded string. If somehow 'i' > was greater than 8 bytes (10 - 2), then the snprintf function would > truncate the string. Increasing the size of the buffer fixes the error.
Get the compiler fixed so that it knows the domain of the value can never exceed the compile-time constant NR_ITERS.
> Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com> > --- > tools/perf/tests/backward-ring-buffer.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c > index 6d598cc071ae..1a9c3becf5ff 100644 > --- a/tools/perf/tests/backward-ring-buffer.c > +++ b/tools/perf/tests/backward-ring-buffer.c > @@ -18,7 +18,7 @@ static void testcase(void) > int i; > > for (i = 0; i < NR_ITERS; i++) { > - char proc_name[10]; > + char proc_name[15];
At least use [16]
> > snprintf(proc_name, sizeof(proc_name), "p:%d\n", i); > prctl(PR_SET_NAME, proc_name); > -- > 2.22.0.657.g960e92d24f-goog
David
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