From: Greg Kroah-Hartman Date: Sat, 9 Oct 2021 15:33:50 +0000 (+0200) Subject: 4.19-stable patches X-Git-Tag: v5.14.12~30 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d3b836b097c69e4b5043d48fbe4afb6a4889cc89;p=thirdparty%2Fkernel%2Fstable-queue.git 4.19-stable patches added patches: bpf-mips-validate-conditional-branch-offsets.patch --- diff --git a/queue-4.19/bpf-mips-validate-conditional-branch-offsets.patch b/queue-4.19/bpf-mips-validate-conditional-branch-offsets.patch new file mode 100644 index 00000000000..b253145cea9 --- /dev/null +++ b/queue-4.19/bpf-mips-validate-conditional-branch-offsets.patch @@ -0,0 +1,267 @@ +From 37cb28ec7d3a36a5bace7063a3dba633ab110f8b Mon Sep 17 00:00:00 2001 +From: Piotr Krysiuk +Date: Wed, 15 Sep 2021 17:04:37 +0100 +Subject: bpf, mips: Validate conditional branch offsets + +From: Piotr Krysiuk + +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 + [] 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 +Signed-off-by: Daniel Borkmann +Tested-by: Johan Almbladh +Acked-by: Johan Almbladh +Cc: Paul Burton +Cc: Thomas Bogendoerfer +Link: https://lore.kernel.org/bpf/20210915160437.4080-1-piotras@gmail.com +Signed-off-by: Ovidiu Panait +Signed-off-by: Greg Kroah-Hartman +--- + 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 */ diff --git a/queue-4.19/series b/queue-4.19/series index 9c856bc4dac..cbdfd1c8dca 100644 --- a/queue-4.19/series +++ b/queue-4.19/series @@ -7,3 +7,4 @@ nfsd4-handle-the-nfsv4-readdir-dircount-hint-being-zero.patch xen-balloon-fix-cancelled-balloon-action.patch arm-dts-omap3430-sdp-fix-nand-device-node.patch arm-dts-qcom-apq8064-use-compatible-which-contains-chipid.patch +bpf-mips-validate-conditional-branch-offsets.patch