Messages in this thread | | | From | Rasmus Villemoes <> | Subject | Re: [PATCH v1 5/7] test_hexdump: check all bytes in real buffer | Date | Thu, 19 Nov 2015 11:11:51 +0100 |
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On Wed, Nov 11 2015, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> After processing by hex_dump_to_buffer() check all the parts to be expected. > > Part 1. The actual expected hex dump with or without ASCII part. > This is provided by plain strcmp() call including check for the > terminating NUL. > > Part 2. Check if the buffer is dirty beyond needed. > We fill the buffer by ' ' (space) characters, so, we expect to have the > tail of buffer will be left untouched. Check all bytes in the tail of > the buffer.
First of all, ' ' is one of the characters which hexdump is certainly supposed to spit out, so I think it's better to use some other character for prefilling. Otherwise we wouldn't be able to detect a stray write of a space which wasn't properly guarded by a size check. I'd suggest '\xff' or any other non-ascii character (and make it a #define so that it's less magic).
> Part 3. Return code should be as expected. > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > --- > lib/test_hexdump.c | 32 ++++++++++++++++---------------- > 1 file changed, 16 insertions(+), 16 deletions(-) > > diff --git a/lib/test_hexdump.c b/lib/test_hexdump.c > index a3e3b01..9b95b67 100644 > --- a/lib/test_hexdump.c > +++ b/lib/test_hexdump.c > @@ -128,10 +128,9 @@ static void __init test_hexdump_set(int rowsize, bool ascii) > > static void __init test_hexdump_overflow(size_t buflen, bool ascii) > { > + char test[TEST_HEXDUMP_BUF_SIZE]; > char buf[TEST_HEXDUMP_BUF_SIZE]; > - const char *t = test_data_1_le[0]; > size_t len = 1; > - size_t l = buflen; > int rs = 16, gs = 1; > int ae, he, e, r; > bool a; > @@ -147,26 +146,27 @@ static void __init test_hexdump_overflow(size_t buflen, bool ascii) > e = ae; > else > e = he; > - buf[e + 2] = '\0'; > > if (!buflen) { > - a = r == e && buf[0] == ' '; > - } else if (l < 3) { > - a = r == e && buf[0] == '\0'; > - } else if (l < 4) { > - a = r == e && !strcmp(buf, t); > - } else if (ascii) { > - if (l < 51) > - a = r == e && buf[l - 1] == '\0' && buf[l - 2] == ' '; > - else > - a = r == e && buf[50] == '\0' && buf[49] == '.'; > + memset(test, ' ', sizeof(test)); > + test[sizeof(buf) - 1] = '\0'; > + > + a = r == e && !memchr_inv(buf, ' ', sizeof(buf));
test and buf happen to have the same size, but "test[sizeof(buf) - 1] = '\0'" is rather odd. But you don't even seem to use test in this branch?
> } else { > - a = r == e && buf[e] == '\0'; > + int f = min_t(int, e + 1, buflen); > + > + test_hexdump_prepare_test(len, rs, gs, test, sizeof(test), ascii); > + test[f - 1] = '\0'; > + > + a = r == e && !memchr_inv(buf + f, ' ', sizeof(buf) - f) && !strcmp(buf, test); > }
There's also a bit of duplication in the !buflen and buflen branches. Why not pull the computation of f (the number of expected bytes written) outside and do
f = min_t(int, e + 1, buflen); a = r == e && !memchr_inv(buf + f, ' ', sizeof(buf) - f); if (buflen) { test_hexdump_prepare_test(len, rs, gs, test, sizeof(test), ascii); test[f - 1] = '\0'; a = a && !memcmp(buf, test, f); }
(I think it's better to use memcmp for "untrusted" buffers - if hexdump didn't make buf into a proper C string, it's a little fragile passing it to strcmp). This makes it obvious that the entire contents of buf is being tested.
Rasmus
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