[NETFILTER]: x_tables: simplify compat API

Split the xt_compat_match/xt_compat_target into smaller type-safe functions
performing just one operation. Handle all alignment and size-related
conversions centrally in these function instead of requiring each module to
implement a full-blown conversion function. Replace ->compat callback by
->compat_from_user and ->compat_to_user callbacks, responsible for
converting just a single private structure.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 133 insertions, 174 deletions

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 673581db986e..800067d69a9a 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -942,73 +942,28 @@ static short compat_calc_jump(u_int16_t offset)
         return delta;
 }
 
-struct compat_ipt_standard_target
+static void compat_standard_from_user(void *dst, void *src)
 {
-        struct compat_xt_entry_target target;
-        compat_int_t verdict;
-};
-
-struct compat_ipt_standard
-{
-        struct compat_ipt_entry entry;
-        struct compat_ipt_standard_target target;
-};
+        int v = *(compat_int_t *)src;
 
-#define IPT_ST_LEN              XT_ALIGN(sizeof(struct ipt_standard_target))
-#define IPT_ST_COMPAT_LEN       COMPAT_XT_ALIGN(sizeof(struct compat_ipt_standard_target))
-#define IPT_ST_OFFSET           (IPT_ST_LEN - IPT_ST_COMPAT_LEN)
+        if (v > 0)
+                v += compat_calc_jump(v);
+        memcpy(dst, &v, sizeof(v));
+}
 
-static int compat_ipt_standard_fn(void *target,
-                void **dstptr, int *size, int convert)
+static int compat_standard_to_user(void __user *dst, void *src)
 {
-        struct compat_ipt_standard_target compat_st, *pcompat_st;
-        struct ipt_standard_target st, *pst;
-        int ret;
+        compat_int_t cv = *(int *)src;
 
-        ret = 0;
-        switch (convert) {
-                case COMPAT_TO_USER:
-                        pst = target;
-                        memcpy(&compat_st.target, &pst->target,
-                                sizeof(compat_st.target));
-                        compat_st.verdict = pst->verdict;
-                        if (compat_st.verdict > 0)
-                                compat_st.verdict -=
-                                        compat_calc_jump(compat_st.verdict);
-                        compat_st.target.u.user.target_size = IPT_ST_COMPAT_LEN;
-                        if (copy_to_user(*dstptr, &compat_st, IPT_ST_COMPAT_LEN))
-                                ret = -EFAULT;
-                        *size -= IPT_ST_OFFSET;
-                        *dstptr += IPT_ST_COMPAT_LEN;
-                        break;
-                case COMPAT_FROM_USER:
-                        pcompat_st = target;
-                        memcpy(&st.target, &pcompat_st->target, IPT_ST_COMPAT_LEN);
-                        st.verdict = pcompat_st->verdict;
-                        if (st.verdict > 0)
-                                st.verdict += compat_calc_jump(st.verdict);
-                        st.target.u.user.target_size = IPT_ST_LEN;
-                        memcpy(*dstptr, &st, IPT_ST_LEN);
-                        *size += IPT_ST_OFFSET;
-                        *dstptr += IPT_ST_LEN;
-                        break;
-                case COMPAT_CALC_SIZE:
-                        *size += IPT_ST_OFFSET;
-                        break;
-                default:
-                        ret = -ENOPROTOOPT;
-                        break;
-        }
-        return ret;
+        if (cv > 0)
+                cv -= compat_calc_jump(cv);
+        return copy_to_user(dst, &cv, sizeof(cv)) ? -EFAULT : 0;
 }
 
 static inline int
 compat_calc_match(struct ipt_entry_match *m, int * size)
 {
-        if (m->u.kernel.match->compat)
-                m->u.kernel.match->compat(m, NULL, size, COMPAT_CALC_SIZE);
-        else
-                xt_compat_match(m, NULL, size, COMPAT_CALC_SIZE);
+        *size += xt_compat_match_offset(m->u.kernel.match);
         return 0;
 }
 
@@ -1023,10 +978,7 @@ static int compat_calc_entry(struct ipt_entry *e, struct xt_table_info *info,
         entry_offset = (void *)e - base;
         IPT_MATCH_ITERATE(e, compat_calc_match, &off);
         t = ipt_get_target(e);
-        if (t->u.kernel.target->compat)
-                t->u.kernel.target->compat(t, NULL, &off, COMPAT_CALC_SIZE);
-        else
-                xt_compat_target(t, NULL, &off, COMPAT_CALC_SIZE);
+        off += xt_compat_target_offset(t->u.kernel.target);
         newinfo->size -= off;
         ret = compat_add_offset(entry_offset, off);
         if (ret)
@@ -1412,17 +1364,13 @@ struct compat_ipt_replace {
 };
 
 static inline int compat_copy_match_to_user(struct ipt_entry_match *m,
-                void __user **dstptr, compat_uint_t *size)
+                void * __user *dstptr, compat_uint_t *size)
 {
-        if (m->u.kernel.match->compat)
-                return m->u.kernel.match->compat(m, dstptr, size,
-                                COMPAT_TO_USER);
-        else
-                return xt_compat_match(m, dstptr, size, COMPAT_TO_USER);
+        return xt_compat_match_to_user(m, dstptr, size);
 }
 
 static int compat_copy_entry_to_user(struct ipt_entry *e,
-                void __user **dstptr, compat_uint_t *size)
+                void * __user *dstptr, compat_uint_t *size)
 {
         struct ipt_entry_target __user *t;
         struct compat_ipt_entry __user *ce;
@@ -1442,11 +1390,7 @@ static int compat_copy_entry_to_user(struct ipt_entry *e,
         if (ret)
                 goto out;
         t = ipt_get_target(e);
-        if (t->u.kernel.target->compat)
-                ret = t->u.kernel.target->compat(t, dstptr, size,
-                                COMPAT_TO_USER);
-        else
-                ret = xt_compat_target(t, dstptr, size, COMPAT_TO_USER);
+        ret = xt_compat_target_to_user(t, dstptr, size);
         if (ret)
                 goto out;
         ret = -EFAULT;
@@ -1478,11 +1422,7 @@ compat_check_calc_match(struct ipt_entry_match *m,
                 return match ? PTR_ERR(match) : -ENOENT;
         }
         m->u.kernel.match = match;
-
-        if (m->u.kernel.match->compat)
-                m->u.kernel.match->compat(m, NULL, size, COMPAT_CALC_SIZE);
-        else
-                xt_compat_match(m, NULL, size, COMPAT_CALC_SIZE);
+        *size += xt_compat_match_offset(match);
 
         (*i)++;
         return 0;
@@ -1543,10 +1483,7 @@ check_compat_entry_size_and_hooks(struct ipt_entry *e,
         }
         t->u.kernel.target = target;
 
-        if (t->u.kernel.target->compat)
-                t->u.kernel.target->compat(t, NULL, &off, COMPAT_CALC_SIZE);
-        else
-                xt_compat_target(t, NULL, &off, COMPAT_CALC_SIZE);
+        off += xt_compat_target_offset(target);
         *size += off;
         ret = compat_add_offset(entry_offset, off);
         if (ret)
@@ -1584,10 +1521,7 @@ static inline int compat_copy_match_from_user(struct ipt_entry_match *m,
 
         dm = (struct ipt_entry_match *)*dstptr;
         match = m->u.kernel.match;
-        if (match->compat)
-                match->compat(m, dstptr, size, COMPAT_FROM_USER);
-        else
-                xt_compat_match(m, dstptr, size, COMPAT_FROM_USER);
+        xt_compat_match_from_user(m, dstptr, size);
 
         ret = xt_check_match(match, AF_INET, dm->u.match_size - sizeof(*dm),
                              name, hookmask, ip->proto,
@@ -1635,10 +1569,7 @@ static int compat_copy_entry_from_user(struct ipt_entry *e, void **dstptr,
         de->target_offset = e->target_offset - (origsize - *size);
         t = ipt_get_target(e);
         target = t->u.kernel.target;
-        if (target->compat)
-                target->compat(t, dstptr, size, COMPAT_FROM_USER);
-        else
-                xt_compat_target(t, dstptr, size, COMPAT_FROM_USER);
+        xt_compat_target_from_user(t, dstptr, size);
 
         de->next_offset = e->next_offset - (origsize - *size);
         for (h = 0; h < NF_IP_NUMHOOKS; h++) {
@@ -2205,7 +2136,9 @@ static struct ipt_target ipt_standard_target = {
         .targetsize     = sizeof(int),
         .family         = AF_INET,
 #ifdef CONFIG_COMPAT
-        .compat         = &compat_ipt_standard_fn,
+        .compatsize     = sizeof(compat_int_t),
+        .compat_from_user = compat_standard_from_user,
+        .compat_to_user = compat_standard_to_user,
 #endif
 };
 
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index be7baf4f6846..58522fc65d33 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -333,52 +333,65 @@ int xt_check_match(const struct xt_match *match, unsigned short family,
 EXPORT_SYMBOL_GPL(xt_check_match);
 
 #ifdef CONFIG_COMPAT
-int xt_compat_match(void *match, void **dstptr, int *size, int convert)
+int xt_compat_match_offset(struct xt_match *match)
 {
-        struct xt_match *m;
-        struct compat_xt_entry_match *pcompat_m;
-        struct xt_entry_match *pm;
-        u_int16_t msize;
-        int off, ret;
+        u_int16_t csize = match->compatsize ? : match->matchsize;
+        return XT_ALIGN(match->matchsize) - COMPAT_XT_ALIGN(csize);
+}
+EXPORT_SYMBOL_GPL(xt_compat_match_offset);
 
-        ret = 0;
-        m = ((struct xt_entry_match *)match)->u.kernel.match;
-        off = XT_ALIGN(m->matchsize) - COMPAT_XT_ALIGN(m->matchsize);
-        switch (convert) {
-                case COMPAT_TO_USER:
-                        pm = (struct xt_entry_match *)match;
-                        msize = pm->u.user.match_size;
-                        if (copy_to_user(*dstptr, pm, msize)) {
-                                ret = -EFAULT;
-                                break;
-                        }
-                        msize -= off;
-                        if (put_user(msize, (u_int16_t *)*dstptr))
-                                ret = -EFAULT;
-                        *size -= off;
-                        *dstptr += msize;
-                        break;
-                case COMPAT_FROM_USER:
-                        pcompat_m = (struct compat_xt_entry_match *)match;
-                        pm = (struct xt_entry_match *)*dstptr;
-                        msize = pcompat_m->u.user.match_size;
-                        memcpy(pm, pcompat_m, msize);
-                        msize += off;
-                        pm->u.user.match_size = msize;
-                        *size += off;
-                        *dstptr += msize;
-                        break;
-                case COMPAT_CALC_SIZE:
-                        *size += off;
-                        break;
-                default:
-                        ret = -ENOPROTOOPT;
-                        break;
+void xt_compat_match_from_user(struct xt_entry_match *m, void **dstptr,
+                               int *size)
+{
+        struct xt_match *match = m->u.kernel.match;
+        struct compat_xt_entry_match *cm = (struct compat_xt_entry_match *)m;
+        int pad, off = xt_compat_match_offset(match);
+        u_int16_t msize = cm->u.user.match_size;
+
+        m = *dstptr;
+        memcpy(m, cm, sizeof(*cm));
+        if (match->compat_from_user)
+                match->compat_from_user(m->data, cm->data);
+        else
+                memcpy(m->data, cm->data, msize - sizeof(*cm));
+        pad = XT_ALIGN(match->matchsize) - match->matchsize;
+        if (pad > 0)
+                memset(m->data + match->matchsize, 0, pad);
+
+        msize += off;
+        m->u.user.match_size = msize;
+
+        *size += off;
+        *dstptr += msize;
+}
+EXPORT_SYMBOL_GPL(xt_compat_match_from_user);
+
+int xt_compat_match_to_user(struct xt_entry_match *m, void __user **dstptr,
+                            int *size)
+{
+        struct xt_match *match = m->u.kernel.match;
+        struct compat_xt_entry_match __user *cm = *dstptr;
+        int off = xt_compat_match_offset(match);
+        u_int16_t msize = m->u.user.match_size - off;
+
+        if (copy_to_user(cm, m, sizeof(*cm)) ||
+            put_user(msize, &cm->u.user.match_size))
+                return -EFAULT;
+
+        if (match->compat_to_user) {
+                if (match->compat_to_user((void __user *)cm->data, m->data))
+                        return -EFAULT;
+        } else {
+                if (copy_to_user(cm->data, m->data, msize - sizeof(*cm)))
+                        return -EFAULT;
         }
-        return ret;
+
+        *size -= off;
+        *dstptr += msize;
+        return 0;
 }
-EXPORT_SYMBOL_GPL(xt_compat_match);
-#endif
+EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
+#endif /* CONFIG_COMPAT */
 
 int xt_check_target(const struct xt_target *target, unsigned short family,
                     unsigned int size, const char *table, unsigned int hook_mask,
@@ -410,51 +423,64 @@ int xt_check_target(const struct xt_target *target, unsigned short family,
 EXPORT_SYMBOL_GPL(xt_check_target);
 
 #ifdef CONFIG_COMPAT
-int xt_compat_target(void *target, void **dstptr, int *size, int convert)
+int xt_compat_target_offset(struct xt_target *target)
 {
-        struct xt_target *t;
-        struct compat_xt_entry_target *pcompat;
-        struct xt_entry_target *pt;
-        u_int16_t tsize;
-        int off, ret;
+        u_int16_t csize = target->compatsize ? : target->targetsize;
+        return XT_ALIGN(target->targetsize) - COMPAT_XT_ALIGN(csize);
+}
+EXPORT_SYMBOL_GPL(xt_compat_target_offset);
 
-        ret = 0;
-        t = ((struct xt_entry_target *)target)->u.kernel.target;
-        off = XT_ALIGN(t->targetsize) - COMPAT_XT_ALIGN(t->targetsize);
-        switch (convert) {
-                case COMPAT_TO_USER:
-                        pt = (struct xt_entry_target *)target;
-                        tsize = pt->u.user.target_size;
-                        if (copy_to_user(*dstptr, pt, tsize)) {
-                                ret = -EFAULT;
-                                break;
-                        }
-                        tsize -= off;
-                        if (put_user(tsize, (u_int16_t *)*dstptr))
-                                ret = -EFAULT;
-                        *size -= off;
-                        *dstptr += tsize;
-                        break;
-                case COMPAT_FROM_USER:
-                        pcompat = (struct compat_xt_entry_target *)target;
-                        pt = (struct xt_entry_target *)*dstptr;
-                        tsize = pcompat->u.user.target_size;
-                        memcpy(pt, pcompat, tsize);
-                        tsize += off;
-                        pt->u.user.target_size = tsize;
-                        *size += off;
-                        *dstptr += tsize;
-                        break;
-                case COMPAT_CALC_SIZE:
-                        *size += off;
-                        break;
-                default:
-                        ret = -ENOPROTOOPT;
-                        break;
+void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr,
+                                int *size)
+{
+        struct xt_target *target = t->u.kernel.target;
+        struct compat_xt_entry_target *ct = (struct compat_xt_entry_target *)t;
+        int pad, off = xt_compat_target_offset(target);
+        u_int16_t tsize = ct->u.user.target_size;
+
+        t = *dstptr;
+        memcpy(t, ct, sizeof(*ct));
+        if (target->compat_from_user)
+                target->compat_from_user(t->data, ct->data);
+        else
+                memcpy(t->data, ct->data, tsize - sizeof(*ct));
+        pad = XT_ALIGN(target->targetsize) - target->targetsize;
+        if (pad > 0)
+                memset(t->data + target->targetsize, 0, pad);
+
+        tsize += off;
+        t->u.user.target_size = tsize;
+
+        *size += off;
+        *dstptr += tsize;
+}
+EXPORT_SYMBOL_GPL(xt_compat_target_from_user);
+
+int xt_compat_target_to_user(struct xt_entry_target *t, void __user **dstptr,
+                             int *size)
+{
+        struct xt_target *target = t->u.kernel.target;
+        struct compat_xt_entry_target __user *ct = *dstptr;
+        int off = xt_compat_target_offset(target);
+        u_int16_t tsize = t->u.user.target_size - off;
+
+        if (copy_to_user(ct, t, sizeof(*ct)) ||
+            put_user(tsize, &ct->u.user.target_size))
+                return -EFAULT;
+
+        if (target->compat_to_user) {
+                if (target->compat_to_user((void __user *)ct->data, t->data))
+                        return -EFAULT;
+        } else {
+                if (copy_to_user(ct->data, t->data, tsize - sizeof(*ct)))
+                        return -EFAULT;
         }
-        return ret;
+
+        *size -= off;
+        *dstptr += tsize;
+        return 0;
 }
-EXPORT_SYMBOL_GPL(xt_compat_target);
+EXPORT_SYMBOL_GPL(xt_compat_target_to_user);
 #endif
 
 struct xt_table_info *xt_alloc_table_info(unsigned int size)