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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Piotr Krysiuk <piotras@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Johan Almbladh <johan.almbladh@anyfinetworks.com>,
	Paul Burton <paulburton@kernel.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Ovidiu Panait <ovidiu.panait@windriver.com>
Subject: [PATCH 5.4 14/52] bpf, mips: Validate conditional branch offsets
Date: Mon, 11 Oct 2021 15:45:43 +0200	[thread overview]
Message-ID: <20211011134504.192578791@linuxfoundation.org> (raw)
In-Reply-To: <20211011134503.715740503@linuxfoundation.org>

From: Piotr Krysiuk <piotras@gmail.com>

commit 37cb28ec7d3a36a5bace7063a3dba633ab110f8b upstream.

The conditional branch instructions on MIPS use 18-bit signed offsets
allowing for a branch range of 128 KBytes (backward and forward).
However, this limit is not observed by the cBPF JIT compiler, and so
the JIT compiler emits out-of-range branches when translating certain
cBPF programs. A specific example of such a cBPF program is included in
the "BPF_MAXINSNS: exec all MSH" test from lib/test_bpf.c that executes
anomalous machine code containing incorrect branch offsets under JIT.

Furthermore, this issue can be abused to craft undesirable machine
code, where the control flow is hijacked to execute arbitrary Kernel
code.

The following steps can be used to reproduce the issue:

  # echo 1 > /proc/sys/net/core/bpf_jit_enable
  # modprobe test_bpf test_name="BPF_MAXINSNS: exec all MSH"

This should produce multiple warnings from build_bimm() similar to:

  ------------[ cut here ]------------
  WARNING: CPU: 0 PID: 209 at arch/mips/mm/uasm-mips.c:210 build_insn+0x558/0x590
  Micro-assembler field overflow
  Modules linked in: test_bpf(+)
  CPU: 0 PID: 209 Comm: modprobe Not tainted 5.14.3 #1
  Stack : 00000000 807bb824 82b33c9c 801843c0 00000000 00000004 00000000 63c9b5ee
          82b33af4 80999898 80910000 80900000 82fd6030 00000001 82b33a98 82087180
          00000000 00000000 80873b28 00000000 000000fc 82b3394c 00000000 2e34312e
          6d6d6f43 809a180f 809a1836 6f6d203a 80900000 00000001 82b33bac 80900000
          00027f80 00000000 00000000 807bb824 00000000 804ed790 001cc317 00000001
  [...]
  Call Trace:
  [<80108f44>] show_stack+0x38/0x118
  [<807a7aac>] dump_stack_lvl+0x5c/0x7c
  [<807a4b3c>] __warn+0xcc/0x140
  [<807a4c3c>] warn_slowpath_fmt+0x8c/0xb8
  [<8011e198>] build_insn+0x558/0x590
  [<8011e358>] uasm_i_bne+0x20/0x2c
  [<80127b48>] build_body+0xa58/0x2a94
  [<80129c98>] bpf_jit_compile+0x114/0x1e4
  [<80613fc4>] bpf_prepare_filter+0x2ec/0x4e4
  [<8061423c>] bpf_prog_create+0x80/0xc4
  [<c0a006e4>] test_bpf_init+0x300/0xba8 [test_bpf]
  [<8010051c>] do_one_initcall+0x50/0x1d4
  [<801c5e54>] do_init_module+0x60/0x220
  [<801c8b20>] sys_finit_module+0xc4/0xfc
  [<801144d0>] syscall_common+0x34/0x58
  [...]
  ---[ end trace a287d9742503c645 ]---

Then the anomalous machine code executes:

=> 0xc0a18000:  addiu   sp,sp,-16
   0xc0a18004:  sw      s3,0(sp)
   0xc0a18008:  sw      s4,4(sp)
   0xc0a1800c:  sw      s5,8(sp)
   0xc0a18010:  sw      ra,12(sp)
   0xc0a18014:  move    s5,a0
   0xc0a18018:  move    s4,zero
   0xc0a1801c:  move    s3,zero

   # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0)
   0xc0a18020:  lui     t6,0x8012
   0xc0a18024:  ori     t4,t6,0x9e14
   0xc0a18028:  li      a1,0
   0xc0a1802c:  jalr    t4
   0xc0a18030:  move    a0,s5
   0xc0a18034:  bnez    v0,0xc0a1ffb8           # incorrect branch offset
   0xc0a18038:  move    v0,zero
   0xc0a1803c:  andi    s4,s3,0xf
   0xc0a18040:  b       0xc0a18048
   0xc0a18044:  sll     s4,s4,0x2
   [...]

   # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0)
   0xc0a1ffa0:  lui     t6,0x8012
   0xc0a1ffa4:  ori     t4,t6,0x9e14
   0xc0a1ffa8:  li      a1,0
   0xc0a1ffac:  jalr    t4
   0xc0a1ffb0:  move    a0,s5
   0xc0a1ffb4:  bnez    v0,0xc0a1ffb8           # incorrect branch offset
   0xc0a1ffb8:  move    v0,zero
   0xc0a1ffbc:  andi    s4,s3,0xf
   0xc0a1ffc0:  b       0xc0a1ffc8
   0xc0a1ffc4:  sll     s4,s4,0x2

   # __BPF_STMT(BPF_LDX | BPF_B | BPF_MSH, 0)
   0xc0a1ffc8:  lui     t6,0x8012
   0xc0a1ffcc:  ori     t4,t6,0x9e14
   0xc0a1ffd0:  li      a1,0
   0xc0a1ffd4:  jalr    t4
   0xc0a1ffd8:  move    a0,s5
   0xc0a1ffdc:  bnez    v0,0xc0a3ffb8           # correct branch offset
   0xc0a1ffe0:  move    v0,zero
   0xc0a1ffe4:  andi    s4,s3,0xf
   0xc0a1ffe8:  b       0xc0a1fff0
   0xc0a1ffec:  sll     s4,s4,0x2
   [...]

   # epilogue
   0xc0a3ffb8:  lw      s3,0(sp)
   0xc0a3ffbc:  lw      s4,4(sp)
   0xc0a3ffc0:  lw      s5,8(sp)
   0xc0a3ffc4:  lw      ra,12(sp)
   0xc0a3ffc8:  addiu   sp,sp,16
   0xc0a3ffcc:  jr      ra
   0xc0a3ffd0:  nop

To mitigate this issue, we assert the branch ranges for each emit call
that could generate an out-of-range branch.

Fixes: 36366e367ee9 ("MIPS: BPF: Restore MIPS32 cBPF JIT")
Fixes: c6610de353da ("MIPS: net: Add BPF JIT")
Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Link: https://lore.kernel.org/bpf/20210915160437.4080-1-piotras@gmail.com
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/mips/net/bpf_jit.c |   57 ++++++++++++++++++++++++++++++++++++------------
 1 file changed, 43 insertions(+), 14 deletions(-)

--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -662,6 +662,11 @@ static void build_epilogue(struct jit_ct
 	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative : func) : \
 	 func##_positive)
 
+static bool is_bad_offset(int b_off)
+{
+	return b_off > 0x1ffff || b_off < -0x20000;
+}
+
 static int build_body(struct jit_ctx *ctx)
 {
 	const struct bpf_prog *prog = ctx->skf;
@@ -728,7 +733,10 @@ load_common:
 			/* Load return register on DS for failures */
 			emit_reg_move(r_ret, r_zero, ctx);
 			/* Return with error */
-			emit_b(b_imm(prog->len, ctx), ctx);
+			b_off = b_imm(prog->len, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_b(b_off, ctx);
 			emit_nop(ctx);
 			break;
 		case BPF_LD | BPF_W | BPF_IND:
@@ -775,8 +783,10 @@ load_ind:
 			emit_jalr(MIPS_R_RA, r_s0, ctx);
 			emit_reg_move(MIPS_R_A0, r_skb, ctx); /* delay slot */
 			/* Check the error value */
-			emit_bcond(MIPS_COND_NE, r_ret, 0,
-				   b_imm(prog->len, ctx), ctx);
+			b_off = b_imm(prog->len, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_bcond(MIPS_COND_NE, r_ret, 0, b_off, ctx);
 			emit_reg_move(r_ret, r_zero, ctx);
 			/* We are good */
 			/* X <- P[1:K] & 0xf */
@@ -855,8 +865,10 @@ load_ind:
 			/* A /= X */
 			ctx->flags |= SEEN_X | SEEN_A;
 			/* Check if r_X is zero */
-			emit_bcond(MIPS_COND_EQ, r_X, r_zero,
-				   b_imm(prog->len, ctx), ctx);
+			b_off = b_imm(prog->len, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_bcond(MIPS_COND_EQ, r_X, r_zero, b_off, ctx);
 			emit_load_imm(r_ret, 0, ctx); /* delay slot */
 			emit_div(r_A, r_X, ctx);
 			break;
@@ -864,8 +876,10 @@ load_ind:
 			/* A %= X */
 			ctx->flags |= SEEN_X | SEEN_A;
 			/* Check if r_X is zero */
-			emit_bcond(MIPS_COND_EQ, r_X, r_zero,
-				   b_imm(prog->len, ctx), ctx);
+			b_off = b_imm(prog->len, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_bcond(MIPS_COND_EQ, r_X, r_zero, b_off, ctx);
 			emit_load_imm(r_ret, 0, ctx); /* delay slot */
 			emit_mod(r_A, r_X, ctx);
 			break;
@@ -926,7 +940,10 @@ load_ind:
 			break;
 		case BPF_JMP | BPF_JA:
 			/* pc += K */
-			emit_b(b_imm(i + k + 1, ctx), ctx);
+			b_off = b_imm(i + k + 1, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_b(b_off, ctx);
 			emit_nop(ctx);
 			break;
 		case BPF_JMP | BPF_JEQ | BPF_K:
@@ -1056,12 +1073,16 @@ jmp_cmp:
 			break;
 		case BPF_RET | BPF_A:
 			ctx->flags |= SEEN_A;
-			if (i != prog->len - 1)
+			if (i != prog->len - 1) {
 				/*
 				 * If this is not the last instruction
 				 * then jump to the epilogue
 				 */
-				emit_b(b_imm(prog->len, ctx), ctx);
+				b_off = b_imm(prog->len, ctx);
+				if (is_bad_offset(b_off))
+					return -E2BIG;
+				emit_b(b_off, ctx);
+			}
 			emit_reg_move(r_ret, r_A, ctx); /* delay slot */
 			break;
 		case BPF_RET | BPF_K:
@@ -1075,7 +1096,10 @@ jmp_cmp:
 				 * If this is not the last instruction
 				 * then jump to the epilogue
 				 */
-				emit_b(b_imm(prog->len, ctx), ctx);
+				b_off = b_imm(prog->len, ctx);
+				if (is_bad_offset(b_off))
+					return -E2BIG;
+				emit_b(b_off, ctx);
 				emit_nop(ctx);
 			}
 			break;
@@ -1133,8 +1157,10 @@ jmp_cmp:
 			/* Load *dev pointer */
 			emit_load_ptr(r_s0, r_skb, off, ctx);
 			/* error (0) in the delay slot */
-			emit_bcond(MIPS_COND_EQ, r_s0, r_zero,
-				   b_imm(prog->len, ctx), ctx);
+			b_off = b_imm(prog->len, ctx);
+			if (is_bad_offset(b_off))
+				return -E2BIG;
+			emit_bcond(MIPS_COND_EQ, r_s0, r_zero, b_off, ctx);
 			emit_reg_move(r_ret, r_zero, ctx);
 			if (code == (BPF_ANC | SKF_AD_IFINDEX)) {
 				BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
@@ -1244,7 +1270,10 @@ void bpf_jit_compile(struct bpf_prog *fp
 
 	/* Generate the actual JIT code */
 	build_prologue(&ctx);
-	build_body(&ctx);
+	if (build_body(&ctx)) {
+		module_memfree(ctx.target);
+		goto out;
+	}
 	build_epilogue(&ctx);
 
 	/* Update the icache */



  parent reply	other threads:[~2021-10-11 13:48 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-11 13:45 [PATCH 5.4 00/52] 5.4.153-rc1 review Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 01/52] Partially revert "usb: Kconfig: using select for USB_COMMON dependency" Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 02/52] USB: cdc-acm: fix racy tty buffer accesses Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 03/52] USB: cdc-acm: fix break reporting Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 04/52] usb: typec: tcpm: handle SRC_STARTUP state if cc changes Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 05/52] xen/privcmd: fix error handling in mmap-resource processing Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 06/52] mmc: meson-gx: do not use memcpy_to/fromio for dram-access-quirk Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 07/52] ovl: fix missing negative dentry check in ovl_rename() Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 08/52] nfsd: fix error handling of register_pernet_subsys() in init_nfsd() Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 09/52] nfsd4: Handle the NFSv4 READDIR dircount hint being zero Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 10/52] xen/balloon: fix cancelled balloon action Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 11/52] ARM: dts: omap3430-sdp: Fix NAND device node Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 12/52] ARM: dts: qcom: apq8064: use compatible which contains chipid Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 13/52] MIPS: BPF: Restore MIPS32 cBPF JIT Greg Kroah-Hartman
2021-10-11 13:45 ` Greg Kroah-Hartman [this message]
2021-10-11 13:45 ` [PATCH 5.4 15/52] soc: qcom: socinfo: Fixed argument passed to platform_set_data() Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 16/52] ARM: dts: qcom: apq8064: Use 27MHz PXO clock as DSI PLL reference Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 17/52] soc: qcom: mdt_loader: Drop PT_LOAD check on hash segment Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 18/52] ARM: dts: imx: Add missing pinctrl-names for panel on M53Menlo Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 19/52] ARM: dts: imx: Fix USB host power regulator polarity " Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 20/52] arm64: dts: qcom: pm8150: use qcom,pm8998-pon binding Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 21/52] xtensa: move XCHAL_KIO_* definitions to kmem_layout.h Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 22/52] xtensa: use CONFIG_USE_OF instead of CONFIG_OF Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 23/52] xtensa: call irqchip_init only when CONFIG_USE_OF is selected Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 24/52] bpf, arm: Fix register clobbering in div/mod implementation Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 25/52] bpf: Fix integer overflow in prealloc_elems_and_freelist() Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 26/52] phy: mdio: fix memory leak Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 27/52] net_sched: fix NULL deref in fifo_set_limit() Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 28/52] powerpc/fsl/dts: Fix phy-connection-type for fm1mac3 Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 29/52] ptp_pch: Load module automatically if ID matches Greg Kroah-Hartman
2021-10-11 13:45 ` [PATCH 5.4 30/52] arm64: dts: freescale: Fix SP805 clock-names Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 31/52] arm64: dts: ls1028a: add missing CAN nodes Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 32/52] ARM: imx6: disable the GIC CPU interface before calling stby-poweroff sequence Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 33/52] net: bridge: use nla_total_size_64bit() in br_get_linkxstats_size() Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 34/52] net/sched: sch_taprio: properly cancel timer from taprio_destroy() Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 35/52] net: sfp: Fix typo in state machine debug string Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 36/52] netlink: annotate data races around nlk->bound Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 37/52] bus: ti-sysc: Use CLKDM_NOAUTO for dra7 dcan1 for errata i893 Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 38/52] video: fbdev: gbefb: Only instantiate device when built for IP32 Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 39/52] drm/nouveau/debugfs: fix file release memory leak Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 40/52] gve: Correct available tx qpl check Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 41/52] rtnetlink: fix if_nlmsg_stats_size() under estimation Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 42/52] gve: fix gve_get_stats() Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 43/52] i40e: fix endless loop under rtnl Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 44/52] i40e: Fix freeing of uninitialized misc IRQ vector Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 45/52] net: prefer socket bound to interface when not in VRF Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 46/52] i2c: acpi: fix resource leak in reconfiguration device addition Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 47/52] bpf, s390: Fix potential memory leak about jit_data Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 48/52] RISC-V: Include clone3() on rv32 Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 49/52] powerpc/bpf: Fix BPF_MOD when imm == 1 Greg Kroah-Hartman
2021-10-11 17:33   ` Naresh Kamboju
2021-10-11 18:24     ` Christophe Leroy
2021-10-12  0:53       ` Sasha Levin
2021-10-12  6:42         ` Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 50/52] x86/platform/olpc: Correct ifdef symbol to intended CONFIG_OLPC_XO15_SCI Greg Kroah-Hartman
2021-10-11 13:46 ` [PATCH 5.4 51/52] x86/hpet: Use another crystalball to evaluate HPET usability Greg Kroah-Hartman
2021-10-11 13:59   ` Jakub Kicinski
2021-10-11 14:05     ` Greg Kroah-Hartman
2021-10-11 14:26       ` Jakub Kicinski
2021-10-11 13:46 ` [PATCH 5.4 52/52] x86/Kconfig: Correct reference to MWINCHIP3D Greg Kroah-Hartman
2021-10-11 15:55 ` [PATCH 5.4 00/52] 5.4.153-rc1 review Florian Fainelli
2021-10-11 17:17 ` Naresh Kamboju
2021-10-12  1:18 ` Shuah Khan
2021-10-12  2:00 ` Guenter Roeck
2021-10-12  8:13 ` Samuel Zou

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