From dc27f3c5d10c58069672215787a96b4fae01818b Mon Sep 17 00:00:00 2001 From: Ondrej Mosnacek Date: Fri, 19 Nov 2021 14:45:20 +0100 Subject: [PATCH] selinux: fix NULL-pointer dereference when hashtab allocation fails 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. Cc: stable@vger.kernel.org Fixes: 03414a49ad5f ("selinux: do not allocate hashtabs dynamically") Signed-off-by: Ondrej Mosnacek Signed-off-by: Paul Moore --- security/selinux/ss/hashtab.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) 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); - h->nel = 0; - if (!h->size) - return 0; + u32 size = hashtab_compute_size(nel_hint); - h->htable = kcalloc(h->size, sizeof(*h->htable), GFP_KERNEL); - return h->htable ? 0 : -ENOMEM; + /* should already be zeroed, but better be safe */ + h->nel = 0; + h->size = 0; + h->htable = NULL; + + 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,