4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Russell King rmk+kernel@armlinux.org.uk
commit 02088d9b392f605c892894b46aa8c83e3abd0115 upstream.
When an eBPF program tail-calls another eBPF program, it enters it after the prologue to avoid having complex stack manipulations. This can lead to kernel oopses, and similar.
Resolve this by always using a fixed stack layout, a CPU register frame pointer, and using this when reloading registers before returning.
Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler") Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm/net/bpf_jit_32.c | 80 ++++++++++++---------------------------------- 1 file changed, 22 insertions(+), 58 deletions(-)
--- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -61,20 +61,24 @@ int bpf_jit_enable __read_mostly; * * high * original ARM_SP => +------------------+ - * | lr | (optional) - * | r4-r8,r10 | callee saved registers - * +------------------+ + * | r4-r8,r10,fp,lr | callee saved registers + * current ARM_FP => +------------------+ * low + * + * When popping registers off the stack at the end of a BPF function, we + * reference them via the current ARM_FP register. */ +#define CALLEE_MASK (1 << ARM_R4 | 1 << ARM_R5 | 1 << ARM_R6 | \ + 1 << ARM_R7 | 1 << ARM_R8 | 1 << ARM_R10 | \ + 1 << ARM_FP) +#define CALLEE_PUSH_MASK (CALLEE_MASK | 1 << ARM_LR) +#define CALLEE_POP_MASK (CALLEE_MASK | 1 << ARM_PC)
#define STACK_OFFSET(k) (k) #define TMP_REG_1 (MAX_BPF_JIT_REG + 0) /* TEMP Register 1 */ #define TMP_REG_2 (MAX_BPF_JIT_REG + 1) /* TEMP Register 2 */ #define TCALL_CNT (MAX_BPF_JIT_REG + 2) /* Tail Call Count */
-/* Flags used for JIT optimization */ -#define SEEN_CALL (1 << 0) - #define FLAG_IMM_OVERFLOW (1 << 0)
/* @@ -135,7 +139,6 @@ static const u8 bpf2a32[][2] = { * idx : index of current last JITed instruction. * prologue_bytes : bytes used in prologue. * epilogue_offset : offset of epilogue starting. - * seen : bit mask used for JIT optimization. * offsets : array of eBPF instruction offsets in * JITed code. * target : final JITed code. @@ -150,7 +153,6 @@ struct jit_ctx { unsigned int idx; unsigned int prologue_bytes; unsigned int epilogue_offset; - u32 seen; u32 flags; u32 *offsets; u32 *target; @@ -340,7 +342,6 @@ static void emit_bx_r(u8 tgt_reg, struct
static inline void emit_blx_r(u8 tgt_reg, struct jit_ctx *ctx) { - ctx->seen |= SEEN_CALL; #if __LINUX_ARM_ARCH__ < 5 emit(ARM_MOV_R(ARM_LR, ARM_PC), ctx); emit_bx_r(tgt_reg, ctx); @@ -403,7 +404,6 @@ static inline void emit_udivmod(u8 rd, u }
/* Call appropriate function */ - ctx->seen |= SEEN_CALL; emit_mov_i(ARM_IP, op == BPF_DIV ? (u32)jit_udiv32 : (u32)jit_mod32, ctx); emit_blx_r(ARM_IP, ctx); @@ -669,8 +669,6 @@ static inline void emit_a32_lsh_r64(cons /* Do LSH operation */ emit(ARM_SUB_I(ARM_IP, rt, 32), ctx); emit(ARM_RSB_I(tmp2[0], rt, 32), ctx); - /* As we are using ARM_LR */ - ctx->seen |= SEEN_CALL; emit(ARM_MOV_SR(ARM_LR, rm, SRTYPE_ASL, rt), ctx); emit(ARM_ORR_SR(ARM_LR, ARM_LR, rd, SRTYPE_ASL, ARM_IP), ctx); emit(ARM_ORR_SR(ARM_IP, ARM_LR, rd, SRTYPE_LSR, tmp2[0]), ctx); @@ -705,8 +703,6 @@ static inline void emit_a32_arsh_r64(con /* Do the ARSH operation */ emit(ARM_RSB_I(ARM_IP, rt, 32), ctx); emit(ARM_SUBS_I(tmp2[0], rt, 32), ctx); - /* As we are using ARM_LR */ - ctx->seen |= SEEN_CALL; emit(ARM_MOV_SR(ARM_LR, rd, SRTYPE_LSR, rt), ctx); emit(ARM_ORR_SR(ARM_LR, ARM_LR, rm, SRTYPE_ASL, ARM_IP), ctx); _emit(ARM_COND_MI, ARM_B(0), ctx); @@ -741,8 +737,6 @@ static inline void emit_a32_lsr_r64(cons /* Do LSH operation */ emit(ARM_RSB_I(ARM_IP, rt, 32), ctx); emit(ARM_SUBS_I(tmp2[0], rt, 32), ctx); - /* As we are using ARM_LR */ - ctx->seen |= SEEN_CALL; emit(ARM_MOV_SR(ARM_LR, rd, SRTYPE_LSR, rt), ctx); emit(ARM_ORR_SR(ARM_LR, ARM_LR, rm, SRTYPE_ASL, ARM_IP), ctx); emit(ARM_ORR_SR(ARM_LR, ARM_LR, rm, SRTYPE_LSR, tmp2[0]), ctx); @@ -877,8 +871,6 @@ static inline void emit_a32_mul_r64(cons /* Do Multiplication */ emit(ARM_MUL(ARM_IP, rd, rn), ctx); emit(ARM_MUL(ARM_LR, rm, rt), ctx); - /* As we are using ARM_LR */ - ctx->seen |= SEEN_CALL; emit(ARM_ADD_R(ARM_LR, ARM_IP, ARM_LR), ctx);
emit(ARM_UMULL(ARM_IP, rm, rd, rt), ctx); @@ -955,7 +947,6 @@ static inline void emit_ar_r(const u8 rd const u8 rn, struct jit_ctx *ctx, u8 op) { switch (op) { case BPF_JSET: - ctx->seen |= SEEN_CALL; emit(ARM_AND_R(ARM_IP, rt, rn), ctx); emit(ARM_AND_R(ARM_LR, rd, rm), ctx); emit(ARM_ORRS_R(ARM_IP, ARM_LR, ARM_IP), ctx); @@ -1119,33 +1110,22 @@ static void build_prologue(struct jit_ct const u8 r2 = bpf2a32[BPF_REG_1][1]; const u8 r3 = bpf2a32[BPF_REG_1][0]; const u8 r4 = bpf2a32[BPF_REG_6][1]; - const u8 r5 = bpf2a32[BPF_REG_6][0]; - const u8 r6 = bpf2a32[TMP_REG_1][1]; - const u8 r7 = bpf2a32[TMP_REG_1][0]; - const u8 r8 = bpf2a32[TMP_REG_2][1]; - const u8 r10 = bpf2a32[TMP_REG_2][0]; const u8 fplo = bpf2a32[BPF_REG_FP][1]; const u8 fphi = bpf2a32[BPF_REG_FP][0]; - const u8 sp = ARM_SP; const u8 *tcc = bpf2a32[TCALL_CNT];
- u16 reg_set = 0; - /* Save callee saved registers. */ - reg_set |= (1<<r4) | (1<<r5) | (1<<r6) | (1<<r7) | (1<<r8) | (1<<r10); #ifdef CONFIG_FRAME_POINTER - reg_set |= (1<<ARM_FP) | (1<<ARM_IP) | (1<<ARM_LR) | (1<<ARM_PC); - emit(ARM_MOV_R(ARM_IP, sp), ctx); + u16 reg_set = CALLEE_PUSH_MASK | 1 << ARM_IP | 1 << ARM_PC; + emit(ARM_MOV_R(ARM_IP, ARM_SP), ctx); emit(ARM_PUSH(reg_set), ctx); emit(ARM_SUB_I(ARM_FP, ARM_IP, 4), ctx); #else - /* Check if call instruction exists in BPF body */ - if (ctx->seen & SEEN_CALL) - reg_set |= (1<<ARM_LR); - emit(ARM_PUSH(reg_set), ctx); + emit(ARM_PUSH(CALLEE_PUSH_MASK), ctx); + emit(ARM_MOV_R(ARM_FP, ARM_SP), ctx); #endif /* Save frame pointer for later */ - emit(ARM_SUB_I(ARM_IP, sp, SCRATCH_SIZE), ctx); + emit(ARM_SUB_I(ARM_IP, ARM_SP, SCRATCH_SIZE), ctx);
ctx->stack_size = imm8m(STACK_SIZE);
@@ -1168,33 +1148,19 @@ static void build_prologue(struct jit_ct /* end of prologue */ }
+/* restore callee saved registers. */ static void build_epilogue(struct jit_ctx *ctx) { - const u8 r4 = bpf2a32[BPF_REG_6][1]; - const u8 r5 = bpf2a32[BPF_REG_6][0]; - const u8 r6 = bpf2a32[TMP_REG_1][1]; - const u8 r7 = bpf2a32[TMP_REG_1][0]; - const u8 r8 = bpf2a32[TMP_REG_2][1]; - const u8 r10 = bpf2a32[TMP_REG_2][0]; - u16 reg_set = 0; - - /* unwind function call stack */ - emit(ARM_ADD_I(ARM_SP, ARM_SP, ctx->stack_size), ctx); - - /* restore callee saved registers. */ - reg_set |= (1<<r4) | (1<<r5) | (1<<r6) | (1<<r7) | (1<<r8) | (1<<r10); #ifdef CONFIG_FRAME_POINTER - /* the first instruction of the prologue was: mov ip, sp */ - reg_set |= (1<<ARM_FP) | (1<<ARM_SP) | (1<<ARM_PC); + /* When using frame pointers, some additional registers need to + * be loaded. */ + u16 reg_set = CALLEE_POP_MASK | 1 << ARM_SP; + emit(ARM_SUB_I(ARM_SP, ARM_FP, hweight16(reg_set) * 4), ctx); emit(ARM_LDM(ARM_SP, reg_set), ctx); #else - if (ctx->seen & SEEN_CALL) - reg_set |= (1<<ARM_PC); /* Restore callee saved registers. */ - emit(ARM_POP(reg_set), ctx); - /* Return back to the callee function */ - if (!(ctx->seen & SEEN_CALL)) - emit_bx_r(ARM_LR, ctx); + emit(ARM_MOV_R(ARM_SP, ARM_FP), ctx); + emit(ARM_POP(CALLEE_POP_MASK), ctx); #endif }
@@ -1422,8 +1388,6 @@ static int build_insn(const struct bpf_i emit_rev32(rt, rt, ctx); goto emit_bswap_uxt; case 64: - /* Because of the usage of ARM_LR */ - ctx->seen |= SEEN_CALL; emit_rev32(ARM_LR, rt, ctx); emit_rev32(rt, rd, ctx); emit(ARM_MOV_R(rd, ARM_LR), ctx);