On Wed, Jan 6, 2021 at 3:13 AM Nicolas Iooss <nicolas.iooss@xxxxxxx> wrote: > > OSS-Fuzz found a NULL pointer dereference when the CIL compiler tries to > compile a policy with an invalid integer: > > $ echo '(ioportcon(2())n)' > tmp.cil > $ secilc tmp.cil > Segmentation fault (core dumped) > > This is because strtol() is called with a NULL pointer, in > cil_fill_integer(). > > Fix this by checking that int_node->data is not NULL. While at it, use > strtoul() instead of strtol() to parse an unsigned integer. > > When using "val > UINT32_MAX" with "unsigned long val;", it is expected > that some compilers emit a warning when the size of "unsigned long" is > 32 bits. In theory gcc could be such a compiler (with warning > -Wtype-limits, which is included in -Wextra). Nevertheless this is > currently broken, according to > https://gcc.gnu.org/pipermail/gcc-help/2021-January/139755.html and > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89126 (this bug was > opened in January 2019). > > In order to prevent this warning from appearing, introduce some > preprocessor macros around the bound check. > > Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28456 > Signed-off-by: Nicolas Iooss <nicolas.iooss@xxxxxxx> Acked-by: James Carter <jwcart2@xxxxxxxxx> > --- > libsepol/cil/src/cil_build_ast.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/libsepol/cil/src/cil_build_ast.c b/libsepol/cil/src/cil_build_ast.c > index be10d61b1314..02481558ad11 100644 > --- a/libsepol/cil/src/cil_build_ast.c > +++ b/libsepol/cil/src/cil_build_ast.c > @@ -5570,19 +5570,27 @@ int cil_fill_integer(struct cil_tree_node *int_node, uint32_t *integer, int base > { > int rc = SEPOL_ERR; > char *endptr = NULL; > - int val; > + unsigned long val; > > - if (int_node == NULL || integer == NULL) { > + if (int_node == NULL || int_node->data == NULL || integer == NULL) { > goto exit; > } > > errno = 0; > - val = strtol(int_node->data, &endptr, base); > + val = strtoul(int_node->data, &endptr, base); > if (errno != 0 || endptr == int_node->data || *endptr != '\0') { > rc = SEPOL_ERR; > goto exit; > } > > + /* Ensure that the value fits a 32-bit integer without triggering -Wtype-limits */ > +#if ULONG_MAX > UINT32_MAX > + if (val > UINT32_MAX) { > + rc = SEPOL_ERR; > + goto exit; > + } > +#endif > + > *integer = val; > > return SEPOL_OK; > @@ -5598,7 +5606,7 @@ int cil_fill_integer64(struct cil_tree_node *int_node, uint64_t *integer, int ba > char *endptr = NULL; > uint64_t val; > > - if (int_node == NULL || integer == NULL) { > + if (int_node == NULL || int_node->data == NULL || integer == NULL) { > goto exit; > } > > -- > 2.30.0 >
