[NET]: More instruction checks fornet/core/filter.c

Signed-off-by: Kris Katterjohn <kjak@users.sourceforge.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 80 insertions, 32 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 3a10e0bc90e8..8964d3445588 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -13,6 +13,7 @@
  * 2 of the License, or (at your option) any later version.
  *
  * Andi Kleen - Fix a few bad bugs and races.
+ * Kris Katterjohn - Added many additional checks in sk_chk_filter()
  */
 
 #include <linux/module.h>
@@ -250,7 +251,7 @@ load_b:
                         mem[fentry->k] = X;
                         continue;
                 default:
-                        /* Invalid instruction counts as RET */
+                        WARN_ON(1);
                         return 0;
                 }
 
@@ -283,8 +284,8 @@ load_b:
  *
  * Check the user's filter code. If we let some ugly
  * filter code slip through kaboom! The filter must contain
- * no references or jumps that are out of range, no illegal instructions
- * and no backward jumps. It must end with a RET instruction
+ * no references or jumps that are out of range, no illegal
+ * instructions, and must end with a RET instruction.
  *
  * Returns 0 if the rule set is legal or a negative errno code if not.
  */
@@ -300,38 +301,85 @@ int sk_chk_filter(struct sock_filter *filter, int flen)
         for (pc = 0; pc < flen; pc++) {
                 /* all jumps are forward as they are not signed */
                 ftest = &filter[pc];
-                if (BPF_CLASS(ftest->code) == BPF_JMP) {
-                        /* but they mustn't jump off the end */
-                        if (BPF_OP(ftest->code) == BPF_JA) {
-                                /*
-                                 * Note, the large ftest->k might cause loops.
-                                 * Compare this with conditional jumps below,
-                                 * where offsets are limited. --ANK (981016)
-                                 */
-                                if (ftest->k >= (unsigned)(flen-pc-1))
-                                        return -EINVAL;
-                        } else {
-                                /* for conditionals both must be safe */
-                                if (pc + ftest->jt +1 >= flen ||
-                                    pc + ftest->jf +1 >= flen)
-                                        return -EINVAL;
-                        }
-                }
 
-                /* check for division by zero   -Kris Katterjohn 2005-10-30 */
-                if (ftest->code == (BPF_ALU|BPF_DIV|BPF_K) && ftest->k == 0)
-                        return -EINVAL;
+                /* Only allow valid instructions */
+                switch (ftest->code) {
+                case BPF_ALU|BPF_ADD|BPF_K:
+                case BPF_ALU|BPF_ADD|BPF_X:
+                case BPF_ALU|BPF_SUB|BPF_K:
+                case BPF_ALU|BPF_SUB|BPF_X:
+                case BPF_ALU|BPF_MUL|BPF_K:
+                case BPF_ALU|BPF_MUL|BPF_X:
+                case BPF_ALU|BPF_DIV|BPF_X:
+                case BPF_ALU|BPF_AND|BPF_K:
+                case BPF_ALU|BPF_AND|BPF_X:
+                case BPF_ALU|BPF_OR|BPF_K:
+                case BPF_ALU|BPF_OR|BPF_X:
+                case BPF_ALU|BPF_LSH|BPF_K:
+                case BPF_ALU|BPF_LSH|BPF_X:
+                case BPF_ALU|BPF_RSH|BPF_K:
+                case BPF_ALU|BPF_RSH|BPF_X:
+                case BPF_ALU|BPF_NEG:
+                case BPF_LD|BPF_W|BPF_ABS:
+                case BPF_LD|BPF_H|BPF_ABS:
+                case BPF_LD|BPF_B|BPF_ABS:
+                case BPF_LD|BPF_W|BPF_LEN:
+                case BPF_LD|BPF_W|BPF_IND:
+                case BPF_LD|BPF_H|BPF_IND:
+                case BPF_LD|BPF_B|BPF_IND:
+                case BPF_LD|BPF_IMM:
+                case BPF_LDX|BPF_W|BPF_LEN:
+                case BPF_LDX|BPF_B|BPF_MSH:
+                case BPF_LDX|BPF_IMM:
+                case BPF_MISC|BPF_TAX:
+                case BPF_MISC|BPF_TXA:
+                case BPF_RET|BPF_K:
+                case BPF_RET|BPF_A:
+                        break;
+
+                /* Some instructions need special checks */
 
-                /* check that memory operations use valid addresses. */
-                if (ftest->k >= BPF_MEMWORDS) {
-                        /* but it might not be a memory operation... */
-                        switch (ftest->code) {
-                        case BPF_ST:    
-                        case BPF_STX:   
-                        case BPF_LD|BPF_MEM:    
-                        case BPF_LDX|BPF_MEM:   
+                case BPF_ALU|BPF_DIV|BPF_K:
+                        /* check for division by zero */
+                        if (ftest->k == 0)
                                 return -EINVAL;
-                        }
+                        break;
+
+                case BPF_LD|BPF_MEM:
+                case BPF_LDX|BPF_MEM:
+                case BPF_ST:
+                case BPF_STX:
+                        /* check for invalid memory addresses */
+                        if (ftest->k >= BPF_MEMWORDS)
+                                return -EINVAL;
+                        break;
+
+                case BPF_JMP|BPF_JA:
+                        /*
+                         * Note, the large ftest->k might cause loops.
+                         * Compare this with conditional jumps below,
+                         * where offsets are limited. --ANK (981016)
+                         */
+                        if (ftest->k >= (unsigned)(flen-pc-1))
+                                return -EINVAL;
+                        break;
+
+                case BPF_JMP|BPF_JEQ|BPF_K:
+                case BPF_JMP|BPF_JEQ|BPF_X:
+                case BPF_JMP|BPF_JGE|BPF_K:
+                case BPF_JMP|BPF_JGE|BPF_X:
+                case BPF_JMP|BPF_JGT|BPF_K:
+                case BPF_JMP|BPF_JGT|BPF_X:
+                case BPF_JMP|BPF_JSET|BPF_K:
+                case BPF_JMP|BPF_JSET|BPF_X:
+                        /* for conditionals both must be safe */
+                        if (pc + ftest->jt + 1 >= flen ||
+                            pc + ftest->jf + 1 >= flen)
+                                return -EINVAL;
+                        break;
+
+                default:
+                        return -EINVAL;
                 }
         }