| Message ID | 20211119134520.943504-1-omosnace@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | selinux: fix NULL-pointer dereference when hashtab allocation fails | expand |
On Fri, Nov 19, 2021 at 8:45 AM Ondrej Mosnacek <omosnace@redhat.com> wrote: > > When the hash table slot array allocation fails in hashtab_init(), > h->size is left initialized with a non-zero value, but the h->htable > pointer is NULL. This may then cause a NULL pointer dereference, since > the policydb code relies on the assumption that even after a failed > hashtab_init(), hashtab_map() and hashtab_destroy() can be safely called > on it. Yet, these detect an empty hashtab only by looking at the size. > > Fix this by making sure that hashtab_init() always leaves behind a valid > empty hashtab when the allocation fails. > > Fixes: 03414a49ad5f ("selinux: do not allocate hashtabs dynamically") > Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com> > --- > security/selinux/ss/hashtab.c | 17 ++++++++++++----- > 1 file changed, 12 insertions(+), 5 deletions(-) Looks good to me, merged into selinux/stable-5.16. However, as it is Friday, I'm going to hold of on sending this to Linus until early next week.
diff --git a/security/selinux/ss/hashtab.c b/security/selinux/ss/hashtab.c index 727c3b484bd3..0ae4e4e57a40 100644 --- a/security/selinux/ss/hashtab.c +++ b/security/selinux/ss/hashtab.c @@ -31,13 +31,20 @@ static u32 hashtab_compute_size(u32 nel) int hashtab_init(struct hashtab *h, u32 nel_hint) { - h->size = hashtab_compute_size(nel_hint); + u32 size = hashtab_compute_size(nel_hint); + + /* should already be zeroed, but better be safe */ h->nel = 0; - if (!h->size) - return 0; + h->size = 0; + h->htable = NULL; - h->htable = kcalloc(h->size, sizeof(*h->htable), GFP_KERNEL); - return h->htable ? 0 : -ENOMEM; + if (size) { + h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL); + if (!h->htable) + return -ENOMEM; + h->size = size; + } + return 0; } int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
When the hash table slot array allocation fails in hashtab_init(), h->size is left initialized with a non-zero value, but the h->htable pointer is NULL. This may then cause a NULL pointer dereference, since the policydb code relies on the assumption that even after a failed hashtab_init(), hashtab_map() and hashtab_destroy() can be safely called on it. Yet, these detect an empty hashtab only by looking at the size. Fix this by making sure that hashtab_init() always leaves behind a valid empty hashtab when the allocation fails. Fixes: 03414a49ad5f ("selinux: do not allocate hashtabs dynamically") Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com> --- security/selinux/ss/hashtab.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)