Patch "ARM: net: bpf: fix LDX instructions" has been added to the 4.14-stable tree

Patch "ARM: net: bpf: fix LDX instructions" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ARM: net: bpf: fix LDX instructions

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-net-bpf-fix-ldx-instructions.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From ec19e02b343db991d2d1610c409efefebf4e2ca9 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Sat, 13 Jan 2018 21:06:16 +0000
Subject: ARM: net: bpf: fix LDX instructions

From: Russell King <rmk+kernel@armlinux.org.uk>

commit ec19e02b343db991d2d1610c409efefebf4e2ca9 upstream.

When the source and destination register are identical, our JIT does not
generate correct code, which leads to kernel oopses.

Fix this by (a) generating more efficient code, and (b) making use of
the temporary earlier if we will overwrite the address register.

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 |   61 ++++++++++++++++++++++++----------------------
 1 file changed, 33 insertions(+), 28 deletions(-)

--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -913,33 +913,53 @@ static inline void emit_str_r(const u8 d
 }
 
 /* dst = *(size*)(src + off) */
-static inline void emit_ldx_r(const u8 dst, const u8 src, bool dstk,
-			      const s32 off, struct jit_ctx *ctx, const u8 sz){
+static inline void emit_ldx_r(const u8 dst[], const u8 src, bool dstk,
+			      s32 off, struct jit_ctx *ctx, const u8 sz){
 	const u8 *tmp = bpf2a32[TMP_REG_1];
-	u8 rd = dstk ? tmp[1] : dst;
+	const u8 *rd = dstk ? tmp : dst;
 	u8 rm = src;
+	s32 off_max;
 
-	if (off) {
+	if (sz == BPF_H)
+		off_max = 0xff;
+	else
+		off_max = 0xfff;
+
+	if (off < 0 || off > off_max) {
 		emit_a32_mov_i(tmp[0], off, false, ctx);
 		emit(ARM_ADD_R(tmp[0], tmp[0], src), ctx);
 		rm = tmp[0];
+		off = 0;
+	} else if (rd[1] == rm) {
+		emit(ARM_MOV_R(tmp[0], rm), ctx);
+		rm = tmp[0];
 	}
 	switch (sz) {
-	case BPF_W:
-		/* Load a Word */
-		emit(ARM_LDR_I(rd, rm, 0), ctx);
+	case BPF_B:
+		/* Load a Byte */
+		emit(ARM_LDRB_I(rd[1], rm, off), ctx);
+		emit_a32_mov_i(dst[0], 0, dstk, ctx);
 		break;
 	case BPF_H:
 		/* Load a HalfWord */
-		emit(ARM_LDRH_I(rd, rm, 0), ctx);
+		emit(ARM_LDRH_I(rd[1], rm, off), ctx);
+		emit_a32_mov_i(dst[0], 0, dstk, ctx);
 		break;
-	case BPF_B:
-		/* Load a Byte */
-		emit(ARM_LDRB_I(rd, rm, 0), ctx);
+	case BPF_W:
+		/* Load a Word */
+		emit(ARM_LDR_I(rd[1], rm, off), ctx);
+		emit_a32_mov_i(dst[0], 0, dstk, ctx);
+		break;
+	case BPF_DW:
+		/* Load a Double Word */
+		emit(ARM_LDR_I(rd[1], rm, off), ctx);
+		emit(ARM_LDR_I(rd[0], rm, off + 4), ctx);
 		break;
 	}
 	if (dstk)
-		emit(ARM_STR_I(rd, ARM_SP, STACK_VAR(dst)), ctx);
+		emit(ARM_STR_I(rd[1], ARM_SP, STACK_VAR(dst[1])), ctx);
+	if (dstk && sz == BPF_DW)
+		emit(ARM_STR_I(rd[0], ARM_SP, STACK_VAR(dst[0])), ctx);
 }
 
 /* Arithmatic Operation */
@@ -1440,22 +1460,7 @@ exit:
 		rn = sstk ? tmp2[1] : src_lo;
 		if (sstk)
 			emit(ARM_LDR_I(rn, ARM_SP, STACK_VAR(src_lo)), ctx);
-		switch (BPF_SIZE(code)) {
-		case BPF_W:
-			/* Load a Word */
-		case BPF_H:
-			/* Load a Half-Word */
-		case BPF_B:
-			/* Load a Byte */
-			emit_ldx_r(dst_lo, rn, dstk, off, ctx, BPF_SIZE(code));
-			emit_a32_mov_i(dst_hi, 0, dstk, ctx);
-			break;
-		case BPF_DW:
-			/* Load a double word */
-			emit_ldx_r(dst_lo, rn, dstk, off, ctx, BPF_W);
-			emit_ldx_r(dst_hi, rn, dstk, off+4, ctx, BPF_W);
-			break;
-		}
+		emit_ldx_r(dst, rn, dstk, off, ctx, BPF_SIZE(code));
 		break;
 	/* R0 = ntohx(*(size *)(((struct sk_buff *)R6)->data + imm)) */
 	case BPF_LD | BPF_ABS | BPF_W:


Patches currently in stable-queue which might be from rmk+kernel@armlinux.org.uk are

queue-4.14/arm-net-bpf-fix-stack-alignment.patch
queue-4.14/arm-net-bpf-fix-ldx-instructions.patch
queue-4.14/arm-net-bpf-fix-register-saving.patch
queue-4.14/arm-net-bpf-move-stack-documentation.patch
queue-4.14/arm-net-bpf-correct-stack-layout-documentation.patch
queue-4.14/arm-net-bpf-clarify-tail_call-index.patch
queue-4.14/arm-net-bpf-avoid-bx-instruction-on-non-thumb-capable-cpus.patch
queue-4.14/arm-net-bpf-fix-tail-call-jumps.patch