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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: 03414a49ad ("selinux: do not allocate hashtabs dynamically")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Ondrej Mosnacek 2021-11-19 14:45:20 +01:00 committed by Paul Moore
parent 32a370abf1
commit dc27f3c5d1
1 changed files with 13 additions and 6 deletions
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19
security/selinux/ss/hashtab.c
View File

@ -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,