Le 05/10/2021 à 22:25, Naveen N. Rao a écrit :
Add checks to ensure that we never emit branch instructions with
truncated branch offsets.

Acked-by: Song Liu <songliubrav...@fb.com>
Acked-by: Johan Almbladh <johan.almbl...@anyfinetworks.com>
Tested-by: Johan Almbladh <johan.almbl...@anyfinetworks.com>
Suggested-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>

Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu>

---
  arch/powerpc/net/bpf_jit.h        | 26 ++++++++++++++++++++------
  arch/powerpc/net/bpf_jit_comp.c   |  6 +++++-
  arch/powerpc/net/bpf_jit_comp32.c |  8 ++++++--
  arch/powerpc/net/bpf_jit_comp64.c |  8 ++++++--
  4 files changed, 37 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h
index 935ea95b66359e..7e9b978b768ed9 100644
--- 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 53aefee3fe70be..fcbf7a917c566e 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -210,7 +210,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
                /* 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 beb12cbc8c2994..a74d52204f8da2 100644
--- 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 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, 
struct codegen_context *
                 */
                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 b87a63dba9c8fb..f06c62089b1457 100644
--- 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 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, 
struct codegen_context *
                 */
                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:

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