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s390 eBPF JIT miscompilation issues fixes.

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These issues can be used by an unprivileged local user to circumvent the verifier and gain root privileges.
 
 v4.1+
 s390/bpf: Fix optimizing out zero-extensions
 s390/bpf: Fix 64-bit subtraction of the -0x80000000 constant
 v5.5+
 s390/bpf: Fix branch shortening during codegen pass
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Merge tag 's390-5.15-ebpf-jit-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

Pull s390 eBPF fixes from Vasily Gorbik:
 "Johan Almbladh has implemented a number of new testcases for eBPF [1],
  which uncovered three miscompilation issues in the s390 eBPF JIT"

Link: https://lore.kernel.org/bpf/20210902185229.1840281-1-johan.almbladh@anyfinetworks.com/ [1]

* tag 's390-5.15-ebpf-jit-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/bpf: Fix optimizing out zero-extensions
  s390/bpf: Fix 64-bit subtraction of the -0x80000000 constant
  s390/bpf: Fix branch shortening during codegen pass
This commit is contained in:
Linus Torvalds 2021-09-21 09:36:11 -07:00
commit 92477dd1fa
1 changed files with 38 additions and 32 deletions
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70
arch/s390/net/bpf_jit_comp.c
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@ -248,8 +248,7 @@ static inline void reg_set_seen(struct bpf_jit *jit, u32 b1)
#define EMIT6_PCREL(op1, op2, b1, b2, i, off, mask) \
({ \
/* Branch instruction needs 6 bytes */ \
int rel = (addrs[(i) + (off) + 1] - (addrs[(i) + 1] - 6)) / 2;\
int rel = (addrs[(i) + (off) + 1] - jit->prg) / 2; \
_EMIT6((op1) | reg(b1, b2) << 16 | (rel & 0xffff), (op2) | (mask));\
REG_SET_SEEN(b1); \
REG_SET_SEEN(b2); \
@ -761,10 +760,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9080000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_ADD | BPF_K: /* dst = (u32) dst + (u32) imm */
if (!imm)
break;
/* alfi %dst,imm */
EMIT6_IMM(0xc20b0000, dst_reg, imm);
if (imm != 0) {
/* alfi %dst,imm */
EMIT6_IMM(0xc20b0000, dst_reg, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_ADD | BPF_K: /* dst = dst + imm */
@ -786,17 +785,22 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9090000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_SUB | BPF_K: /* dst = (u32) dst - (u32) imm */
if (!imm)
break;
/* alfi %dst,-imm */
EMIT6_IMM(0xc20b0000, dst_reg, -imm);
if (imm != 0) {
/* alfi %dst,-imm */
EMIT6_IMM(0xc20b0000, dst_reg, -imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_SUB | BPF_K: /* dst = dst - imm */
if (!imm)
break;
/* agfi %dst,-imm */
EMIT6_IMM(0xc2080000, dst_reg, -imm);
if (imm == -0x80000000) {
/* algfi %dst,0x80000000 */
EMIT6_IMM(0xc20a0000, dst_reg, 0x80000000);
} else {
/* agfi %dst,-imm */
EMIT6_IMM(0xc2080000, dst_reg, -imm);
}
break;
/*
* BPF_MUL
@ -811,10 +815,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb90c0000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_MUL | BPF_K: /* dst = (u32) dst * (u32) imm */
if (imm == 1)
break;
/* msfi %r5,imm */
EMIT6_IMM(0xc2010000, dst_reg, imm);
if (imm != 1) {
/* msfi %r5,imm */
EMIT6_IMM(0xc2010000, dst_reg, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_MUL | BPF_K: /* dst = dst * imm */
@ -867,6 +871,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
if (BPF_OP(insn->code) == BPF_MOD)
/* lhgi %dst,0 */
EMIT4_IMM(0xa7090000, dst_reg, 0);
else
EMIT_ZERO(dst_reg);
break;
}
/* lhi %w0,0 */
@ -999,10 +1005,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9820000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_XOR | BPF_K: /* dst = (u32) dst ^ (u32) imm */
if (!imm)
break;
/* xilf %dst,imm */
EMIT6_IMM(0xc0070000, dst_reg, imm);
if (imm != 0) {
/* xilf %dst,imm */
EMIT6_IMM(0xc0070000, dst_reg, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_XOR | BPF_K: /* dst = dst ^ imm */
@ -1033,10 +1039,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT6_DISP_LH(0xeb000000, 0x000d, dst_reg, dst_reg, src_reg, 0);
break;
case BPF_ALU | BPF_LSH | BPF_K: /* dst = (u32) dst << (u32) imm */
if (imm == 0)
break;
/* sll %dst,imm(%r0) */
EMIT4_DISP(0x89000000, dst_reg, REG_0, imm);
if (imm != 0) {
/* sll %dst,imm(%r0) */
EMIT4_DISP(0x89000000, dst_reg, REG_0, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_LSH | BPF_K: /* dst = dst << imm */
@ -1058,10 +1064,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT6_DISP_LH(0xeb000000, 0x000c, dst_reg, dst_reg, src_reg, 0);
break;
case BPF_ALU | BPF_RSH | BPF_K: /* dst = (u32) dst >> (u32) imm */
if (imm == 0)
break;
/* srl %dst,imm(%r0) */
EMIT4_DISP(0x88000000, dst_reg, REG_0, imm);
if (imm != 0) {
/* srl %dst,imm(%r0) */
EMIT4_DISP(0x88000000, dst_reg, REG_0, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_RSH | BPF_K: /* dst = dst >> imm */
@ -1083,10 +1089,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT6_DISP_LH(0xeb000000, 0x000a, dst_reg, dst_reg, src_reg, 0);
break;
case BPF_ALU | BPF_ARSH | BPF_K: /* ((s32) dst >> imm */
if (imm == 0)
break;
/* sra %dst,imm(%r0) */
EMIT4_DISP(0x8a000000, dst_reg, REG_0, imm);
if (imm != 0) {
/* sra %dst,imm(%r0) */
EMIT4_DISP(0x8a000000, dst_reg, REG_0, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_ARSH | BPF_K: /* ((s64) dst) >>= imm */