On Tue, Aug 01, 2023 at 07:30:16AM +0200, Thomas Weißschuh wrote:
If read() fails and returns -1 buf would be accessed out of bounds.
Signed-off-by: Thomas Weißschuh linux@weissschuh.net
tools/testing/selftests/nolibc/nolibc-test.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index 82714051c72f..a334f8450a34 100644 --- a/tools/testing/selftests/nolibc/nolibc-test.c +++ b/tools/testing/selftests/nolibc/nolibc-test.c @@ -1031,6 +1031,12 @@ static int expect_vfprintf(int llen, int c, const char *expected, const char *fm lseek(fd, 0, SEEK_SET); r = read(fd, buf, sizeof(buf) - 1);
- if (r == -1) {
llen += printf(" read() = %s", errorname(errno));result(llen, FAIL);return 1;- }
- buf[r] = '\0';
In fact given the nature of this file (test if we properly implemented our syscalls), I think that a more conservative approach is deserved because if we messed up on read() we can have anything on return and we don't want to trust that. As such I would suggest that we declare r as ssize_t and verify that it's neither negative nor larger than sizeof(buf)-1, which becomes:
if ((size_t)r >= sizeof(buf)) { ... fail ... }
You'll also have to turn w to ssize_t then due to the test later BTW.
Willy