On Wed, Apr 28, 2021 at 9:04 PM Niteesh G. S. <niteesh...@gmail.com> wrote: > > > > On Thu, Apr 29, 2021 at 12:50 AM Gedare Bloom <ged...@rtems.org> wrote: >> >> On Wed, Apr 28, 2021 at 11:30 AM G S Niteesh Babu <niteesh...@gmail.com> >> wrote: >> > >> > This patch adds asserts to fix coverity defects >> > 1) CID 1474437 (Out-of-bounds access) >> > 2) CID 1474436 (Out-of-bounds access) >> > >> > From manual inspection, out of bounds access cannot occur due to >> > bounds checking but coverity fails to detect the checks. >> > We are adding asserts as a secondary check. >> > --- >> > bsps/shared/ofw/ofw.c | 12 +++++++++++- >> > 1 file changed, 11 insertions(+), 1 deletion(-) >> > >> > diff --git a/bsps/shared/ofw/ofw.c b/bsps/shared/ofw/ofw.c >> > index f4b8b63931..808fa85d81 100644 >> > --- a/bsps/shared/ofw/ofw.c >> > +++ b/bsps/shared/ofw/ofw.c >> > @@ -42,6 +42,7 @@ >> > #include <assert.h> >> > #include <rtems/sysinit.h> >> > #include <ofw/ofw_test.h> >> > +#include <rtems/score/assert.h> >> > >> > static void *fdtp = NULL; >> > >> > @@ -186,6 +187,7 @@ ssize_t rtems_ofw_get_prop( >> > const void *prop; >> > int offset; >> > int len; >> > + int copy_len; >> > uint32_t cpuid; >> > >> > offset = rtems_fdt_phandle_to_offset(node); >> > @@ -226,7 +228,9 @@ ssize_t rtems_ofw_get_prop( >> > return -1; >> > } >> > >> > - bcopy(prop, buf, MIN(len, bufsize)); >> > + copy_len = MIN(len, bufsize); >> > + _Assert(copy_len <= bufsize); >> > + memmove(prop, buf, copy_len); >> > >> > return len; >> > } >> > @@ -637,6 +641,12 @@ int rtems_ofw_get_reg( >> > range.child_bus = fdt32_to_cpu(ptr[j].child_bus); >> > range.size = fdt32_to_cpu(ptr[j].size); >> > >> > + /* >> > + * buf[i + 1] should upperbound the access for buf[i]. >> > + * Thus by making sure buf[i + 1] <= (buf + size) we >> > + * can be sure buf[i] will always be inbounds. >> > + */ >> > + _Assert(buf[i + 1] <= (buf + size)); >> This looks suspect. It can make an out-of-bounds read access I think. How >> about >> _Assert(i < size); >> Is that equivalent? > > No that won't work because size is the length of the buffer in bytes. I right > thing would be > _Assert(i < nregs) where nregs = size / sizeof(rtems_ofw_reg) You can also do this generically with size / sizeof(buf[0]). We might have such helpers already for array / address calculations, I'm not sure.
> but I don't think adding this will make any change. > BTW what makes you suspect that it can still make an out-of-bounds access? I meant that buf[i+1] is out of range if (i >= size - 1). However, even then the logic is suspicious, you're comparing the value at buf[i+1] to the address of buf+size. What you mean is &buf[i+1] <= (buf+size). This actually might not be an out-of-bounds access then, I think you can do this safely since you don't dereference *(buf + i + 1). Is it also correct to use &buf[i] < (buf+size)? That will be better than testing equality. Or, use &buf[i] < (buf + size - (sizeof(buf[0]) - 1)) since what you really want to confirm is that buf[i] is not going to access any bytes past the buf+size. >> >> >> > if (buf[i].start >= range.child_bus && >> > buf[i].start < range.child_bus + range.size) { >> > offset = range.parent_bus - range.child_bus; >> > -- >> > 2.17.1 >> > >> > _______________________________________________ >> > devel mailing list >> > devel@rtems.org >> > http://lists.rtems.org/mailman/listinfo/devel _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel