From 3832ba4e283d7052b783dab8311df7e3590fed93 Mon Sep 17 00:00:00 2001
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date: Wed, 6 Oct 2021 01:55:21 +0530
Subject: [PATCH] powerpc/bpf: Validate branch ranges
References: bsc#1188983 CVE-2021-34556 bsc#1188985 CVE-2021-35477
Patch-mainline: v5.15-rc5
Git-commit: 3832ba4e283d7052b783dab8311df7e3590fed93
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
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
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
--- a/arch/powerpc/net/bpf_jit.h
+++ b/arch/powerpc/net/bpf_jit.h
@@ -24,13 +24,27 @@
#define PPC_NEG(d, a) EMIT(PPC_INST_NEG | ___PPC_RT(d) | ___PPC_RA(a))
/* 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)
+
/* "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
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.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);
+ if (bpf_jit_build_body(fp, code_base, &cgctx, addrs)) {
+ bpf_jit_binary_free(bpf_hdr);
+ fp = org_fp;
+ goto out;
+ }
bpf_jit_build_epilogue(code_base, &cgctx);
if (bpf_jit_enable > 1)
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
--- 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
PPC_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);
PPC_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:
--
2.31.1