netfilter: compat: reject huge allocation requests

no need to bother even trying to allocating huge compat offset arrays,
such ruleset is rejected later on anyway becaus we refuse to allocate
overly large rule blobs.

However, compat translation happens before blob allocation, so we should
add a check there too.

This is supposed to help with fuzzing by avoiding oom-killer.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index e878c85a9268058fc4beee3cc2c00e400d086d57..33724b08b8f0366ec0cde15eb829614dbe74ae85 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -582,14 +582,8 @@ int xt_compat_add_offset(u_int8_t af, unsigned int offset, int delta)
 {
        struct xt_af *xp = &xt[af];
 
-       if (!xp->compat_tab) {
-               if (!xp->number)
-                       return -EINVAL;
-               xp->compat_tab = vmalloc(sizeof(struct compat_delta) * xp->number);
-               if (!xp->compat_tab)
-                       return -ENOMEM;
-               xp->cur = 0;
-       }
+       if (WARN_ON(!xp->compat_tab))
+               return -ENOMEM;
 
        if (xp->cur >= xp->number)
                return -EINVAL;
@@ -634,6 +628,22 @@ EXPORT_SYMBOL_GPL(xt_compat_calc_jump);
 
 int xt_compat_init_offsets(u8 af, unsigned int number)
 {
+       size_t mem;
+
+       if (!number || number > (INT_MAX / sizeof(struct compat_delta)))
+               return -EINVAL;
+
+       if (WARN_ON(xt[af].compat_tab))
+               return -EINVAL;
+
+       mem = sizeof(struct compat_delta) * number;
+       if (mem > XT_MAX_TABLE_SIZE)
+               return -ENOMEM;
+
+       xt[af].compat_tab = vmalloc(mem);
+       if (!xt[af].compat_tab)
+               return -ENOMEM;
+
        xt[af].number = number;
        xt[af].cur = 0;