On Wed, Dec 30, 2020 at 4:09 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. > > Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=28456 > Signed-off-by: Nicolas Iooss <nicolas.iooss@xxxxxxx> > --- > libsepol/cil/src/cil_build_ast.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/libsepol/cil/src/cil_build_ast.c b/libsepol/cil/src/cil_build_ast.c > index 67801def0dc0..0c9015cef578 100644 > --- a/libsepol/cil/src/cil_build_ast.c > +++ b/libsepol/cil/src/cil_build_ast.c > @@ -5566,15 +5566,15 @@ 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); > - if (errno != 0 || endptr == int_node->data || *endptr != '\0') { > + val = strtoul(int_node->data, &endptr, base); > + if (errno != 0 || endptr == int_node->data || *endptr != '\0' || val > UINT32_MAX) { I wonder if compilers/static analysis tools will balk on this as strtoul's return, an unsigned long, on a 32 bit machine will be 32 bits, so this could have a dead expression as val > UINT32_MAX will always be false. Perhaps use the strtoull variant to always have 64 bits? > rc = SEPOL_ERR; > goto exit; > } > @@ -5594,7 +5594,7 @@ 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; > } > > -- > 2.29.2 >
