powerpc/bpf: Validate branch ranges

Add checks to ensure that we never emit branch instructions with
truncated branch offsets.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/71d33a6b7603ec1013c9734dd8bdd4ff5e929142.1633464148.git.naveen.n.rao@linux.vnet.ibm.com

diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 935ea95..7e9b978 100644 (file)
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -24,16 +24,30 @@
 #define EMIT(instr)            PLANT_INSTR(image, ctx->idx, instr)
 
 /* Long jump; (unconditional 'branch') */
-#define PPC_JMP(dest)          EMIT(PPC_INST_BRANCH |                        \
-                                    (((dest) - (ctx->idx * 4)) & 0x03fffffc))
+#define PPC_JMP(dest)                                                        \
+       do {                                                                  \
+               long offset = (long)(dest) - (ctx->idx * 4);                  \
+               if (!is_offset_in_branch_range(offset)) {                     \
+                       pr_err_ratelimited("Branch offset 0x%lx (@%u) out of range\n", offset, ctx->idx);                       \
+                       return -ERANGE;                                       \
+               }                                                             \
+               EMIT(PPC_INST_BRANCH | (offset & 0x03fffffc));                \
+       } while (0)
+
 /* blr; (unconditional 'branch' with link) to absolute address */
 #define PPC_BL_ABS(dest)       EMIT(PPC_INST_BL |                            \
                                     (((dest) - (unsigned long)(image + ctx->idx)) & 0x03fffffc))
 /* "cond" here covers BO:BI fields. */
-#define PPC_BCC_SHORT(cond, dest)      EMIT(PPC_INST_BRANCH_COND |           \
-                                            (((cond) & 0x3ff) << 16) |       \
-                                            (((dest) - (ctx->idx * 4)) &     \
-                                             0xfffc))
+#define PPC_BCC_SHORT(cond, dest)                                            \
+       do {                                                                  \
+               long offset = (long)(dest) - (ctx->idx * 4);                  \
+               if (!is_offset_in_cond_branch_range(offset)) {                \
+                       pr_err_ratelimited("Conditional branch offset 0x%lx (@%u) out of range\n", offset, ctx->idx);           \
+                       return -ERANGE;                                       \
+               }                                                             \
+               EMIT(PPC_INST_BRANCH_COND | (((cond) & 0x3ff) << 16) | (offset & 0xfffc));                                      \
+       } while (0)
+
 /* Sign-extended 32-bit immediate load */
 #define PPC_LI32(d, i)         do {                                          \
                if ((int)(uintptr_t)(i) >= -32768 &&                          \

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 53aefee..fcbf7a9 100644 (file)
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -210,7 +210,11 @@ skip_init_ctx:
                /* Now build the prologue, body code & epilogue for real. */
                cgctx.idx = 0;
                bpf_jit_build_prologue(code_base, &cgctx);
-               bpf_jit_build_body(fp, code_base, &cgctx, addrs, extra_pass);
+               if (bpf_jit_build_body(fp, code_base, &cgctx, addrs, extra_pass)) {
+                       bpf_jit_binary_free(bpf_hdr);
+                       fp = org_fp;
+                       goto out_addrs;
+               }
                bpf_jit_build_epilogue(code_base, &cgctx);
 
                if (bpf_jit_enable > 1)

diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c
index beb12cb..a74d522 100644 (file)
--- a/arch/powerpc/net/bpf_jit_comp32.c
+++ b/arch/powerpc/net/bpf_jit_comp32.c
@@ -200,7 +200,7 @@ void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 fun
        }
 }
 
-static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
+static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
 {
        /*
         * By now, the eBPF program has already setup parameters in r3-r6
@@ -261,7 +261,9 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32
        bpf_jit_emit_common_epilogue(image, ctx);
 
        EMIT(PPC_RAW_BCTR());
+
        /* out: */
+       return 0;
 }
 
 /* Assemble the body code between the prologue & epilogue */
@@ -1090,7 +1092,9 @@ cond_branch:
                 */
                case BPF_JMP | BPF_TAIL_CALL:
                        ctx->seen |= SEEN_TAILCALL;
-                       bpf_jit_emit_tail_call(image, ctx, addrs[i + 1]);
+                       ret = bpf_jit_emit_tail_call(image, ctx, addrs[i + 1]);
+                       if (ret < 0)
+                               return ret;
                        break;
 
                default:

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index b87a63d..f06c620 100644 (file)
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -206,7 +206,7 @@ void bpf_jit_emit_func_call_rel(u32 *image, struct codegen_context *ctx, u64 fun
        EMIT(PPC_RAW_BCTRL());
 }
 
-static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
+static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 out)
 {
        /*
         * By now, the eBPF program has already setup parameters in r3, r4 and r5
@@ -267,7 +267,9 @@ static void bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32
        bpf_jit_emit_common_epilogue(image, ctx);
 
        EMIT(PPC_RAW_BCTR());
+
        /* out: */
+       return 0;
 }
 
 /* Assemble the body code between the prologue & epilogue */
@@ -993,7 +995,9 @@ cond_branch:
                 */
                case BPF_JMP | BPF_TAIL_CALL:
                        ctx->seen |= SEEN_TAILCALL;
-                       bpf_jit_emit_tail_call(image, ctx, addrs[i + 1]);
+                       ret = bpf_jit_emit_tail_call(image, ctx, addrs[i + 1]);
+                       if (ret < 0)
+                               return ret;
                        break;
 
                default: