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-rw-r--r--arch/x86/net/bpf_jit_comp.c63
-rw-r--r--include/linux/filter.h1
-rw-r--r--kernel/bpf/core.c9
-rw-r--r--kernel/bpf/verifier.c30
-rw-r--r--tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c3
5 files changed, 74 insertions, 32 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index df5fac428408fe..59cbc94b6e6903 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1807,36 +1807,41 @@ populate_extable:
if (BPF_MODE(insn->code) == BPF_PROBE_MEM ||
BPF_MODE(insn->code) == BPF_PROBE_MEMSX) {
/* Conservatively check that src_reg + insn->off is a kernel address:
- * src_reg + insn->off >= TASK_SIZE_MAX + PAGE_SIZE
- * src_reg is used as scratch for src_reg += insn->off and restored
- * after emit_ldx if necessary
+ * src_reg + insn->off > TASK_SIZE_MAX + PAGE_SIZE
+ * and
+ * src_reg + insn->off < VSYSCALL_ADDR
*/
- u64 limit = TASK_SIZE_MAX + PAGE_SIZE;
+ u64 limit = TASK_SIZE_MAX + PAGE_SIZE - VSYSCALL_ADDR;
u8 *end_of_jmp;
- /* At end of these emitted checks, insn->off will have been added
- * to src_reg, so no need to do relative load with insn->off offset
- */
- insn_off = 0;
+ /* movabsq r10, VSYSCALL_ADDR */
+ emit_mov_imm64(&prog, BPF_REG_AX, (long)VSYSCALL_ADDR >> 32,
+ (u32)(long)VSYSCALL_ADDR);
- /* movabsq r11, limit */
- EMIT2(add_1mod(0x48, AUX_REG), add_1reg(0xB8, AUX_REG));
- EMIT((u32)limit, 4);
- EMIT(limit >> 32, 4);
+ /* mov src_reg, r11 */
+ EMIT_mov(AUX_REG, src_reg);
if (insn->off) {
- /* add src_reg, insn->off */
- maybe_emit_1mod(&prog, src_reg, true);
- EMIT2_off32(0x81, add_1reg(0xC0, src_reg), insn->off);
+ /* add r11, insn->off */
+ maybe_emit_1mod(&prog, AUX_REG, true);
+ EMIT2_off32(0x81, add_1reg(0xC0, AUX_REG), insn->off);
}
- /* cmp src_reg, r11 */
- maybe_emit_mod(&prog, src_reg, AUX_REG, true);
- EMIT2(0x39, add_2reg(0xC0, src_reg, AUX_REG));
+ /* sub r11, r10 */
+ maybe_emit_mod(&prog, AUX_REG, BPF_REG_AX, true);
+ EMIT2(0x29, add_2reg(0xC0, AUX_REG, BPF_REG_AX));
+
+ /* movabsq r10, limit */
+ emit_mov_imm64(&prog, BPF_REG_AX, (long)limit >> 32,
+ (u32)(long)limit);
+
+ /* cmp r10, r11 */
+ maybe_emit_mod(&prog, AUX_REG, BPF_REG_AX, true);
+ EMIT2(0x39, add_2reg(0xC0, AUX_REG, BPF_REG_AX));
- /* if unsigned '>=', goto load */
- EMIT2(X86_JAE, 0);
+ /* if unsigned '>', goto load */
+ EMIT2(X86_JA, 0);
end_of_jmp = prog;
/* xor dst_reg, dst_reg */
@@ -1862,18 +1867,6 @@ populate_extable:
/* populate jmp_offset for JMP above */
start_of_ldx[-1] = prog - start_of_ldx;
- if (insn->off && src_reg != dst_reg) {
- /* sub src_reg, insn->off
- * Restore src_reg after "add src_reg, insn->off" in prev
- * if statement. But if src_reg == dst_reg, emit_ldx
- * above already clobbered src_reg, so no need to restore.
- * If add src_reg, insn->off was unnecessary, no need to
- * restore either.
- */
- maybe_emit_1mod(&prog, src_reg, true);
- EMIT2_off32(0x81, add_1reg(0xE8, src_reg), insn->off);
- }
-
if (!bpf_prog->aux->extable)
break;
@@ -3473,3 +3466,9 @@ bool bpf_jit_supports_ptr_xchg(void)
{
return true;
}
+
+/* x86-64 JIT emits its own code to filter user addresses so return 0 here */
+u64 bpf_arch_uaddress_limit(void)
+{
+ return 0;
+}
diff --git a/include/linux/filter.h b/include/linux/filter.h
index c99bc3df2d28e3..219ee7a7687443 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -963,6 +963,7 @@ bool bpf_jit_supports_far_kfunc_call(void);
bool bpf_jit_supports_exceptions(void);
bool bpf_jit_supports_ptr_xchg(void);
bool bpf_jit_supports_arena(void);
+u64 bpf_arch_uaddress_limit(void);
void arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, u64 bp), void *cookie);
bool bpf_helper_changes_pkt_data(void *func);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 696bc55de8e82e..1ea5ce5bb59933 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2942,6 +2942,15 @@ bool __weak bpf_jit_supports_arena(void)
return false;
}
+u64 __weak bpf_arch_uaddress_limit(void)
+{
+#if defined(CONFIG_64BIT) && defined(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE)
+ return TASK_SIZE;
+#else
+ return 0;
+#endif
+}
+
/* Return TRUE if the JIT backend satisfies the following two conditions:
* 1) JIT backend supports atomic_xchg() on pointer-sized words.
* 2) Under the specific arch, the implementation of xchg() is the same
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index aa24beb65393c8..cb7ad1f795e18b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19675,6 +19675,36 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
goto next_insn;
}
+ /* Make it impossible to de-reference a userspace address */
+ if (BPF_CLASS(insn->code) == BPF_LDX &&
+ (BPF_MODE(insn->code) == BPF_PROBE_MEM ||
+ BPF_MODE(insn->code) == BPF_PROBE_MEMSX)) {
+ struct bpf_insn *patch = &insn_buf[0];
+ u64 uaddress_limit = bpf_arch_uaddress_limit();
+
+ if (!uaddress_limit)
+ goto next_insn;
+
+ *patch++ = BPF_MOV64_REG(BPF_REG_AX, insn->src_reg);
+ if (insn->off)
+ *patch++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_AX, insn->off);
+ *patch++ = BPF_ALU64_IMM(BPF_RSH, BPF_REG_AX, 32);
+ *patch++ = BPF_JMP_IMM(BPF_JLE, BPF_REG_AX, uaddress_limit >> 32, 2);
+ *patch++ = *insn;
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = BPF_MOV64_IMM(insn->dst_reg, 0);
+
+ cnt = patch - insn_buf;
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
+ if (!new_prog)
+ return -ENOMEM;
+
+ delta += cnt - 1;
+ env->prog = prog = new_prog;
+ insn = new_prog->insnsi + i + delta;
+ goto next_insn;
+ }
+
/* Implement LD_ABS and LD_IND with a rewrite, if supported by the program type. */
if (BPF_CLASS(insn->code) == BPF_LD &&
(BPF_MODE(insn->code) == BPF_ABS ||
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 39ad96a18123f6..edcd26106557b4 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -205,6 +205,9 @@ __weak noinline struct file *bpf_testmod_return_ptr(int arg)
case 5: return (void *)~(1ull << 30); /* trigger extable */
case 6: return &f; /* valid addr */
case 7: return (void *)((long)&f | 1); /* kernel tricks */
+#ifdef CONFIG_X86_64
+ case 8: return (void *)VSYSCALL_ADDR; /* vsyscall page address */
+#endif
default: return NULL;
}
}
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-29 09:12:30 +0000