| Message ID | 20230801-nolibc-warnings-v2-9-1ba5ca57bd9b@weissschuh.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | tools/nolibc: enable compiler warnings | expand |
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
On 2023-08-01 08:59:17+0200, Willy Tarreau wrote: > 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 ... > } As r == w is validated just below anyways we could move the assignment buf[r] = '\0' after that check and then we don't need a new block. > You'll also have to turn w to ssize_t then due to the test later BTW. Will do in any case.
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'; fclose(memfile);
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(+)