@@ -563,6 +563,7 @@ struct bpf_insn_aux_data {
u64 map_key_state; /* constant (32 bit) key tracking for maps */
int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
u32 seen; /* this insn was processed by the verifier at env->pass_cnt */
+ bool nospec; /* do not execute this instruction speculatively */
bool nospec_result; /* result is unsafe under speculation, nospec must follow */
bool zext_dst; /* this insn zero extends dst reg */
bool needs_zext; /* alu op needs to clear upper bits */
@@ -1990,6 +1990,18 @@ static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx,
return 0;
}
+static bool error_recoverable_with_nospec(int err)
+{
+ /* Should only return true for non-fatal errors that are allowed to
+ * occur during speculative verification. For these we can insert a
+ * nospec and the program might still be accepted. Do not include
+ * something like ENOMEM because it is likely to re-occur for the next
+ * architectural path once it has been recovered-from in all speculative
+ * paths.
+ */
+ return err == -EPERM || err == -EACCES || err == -EINVAL;
+}
+
static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
int insn_idx, int prev_insn_idx,
bool speculative)
@@ -11084,7 +11096,7 @@ static int check_get_func_ip(struct bpf_verifier_env *env)
return -ENOTSUPP;
}
-static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
+static struct bpf_insn_aux_data *cur_aux(const struct bpf_verifier_env *env)
{
return &env->insn_aux_data[env->insn_idx];
}
@@ -13828,7 +13840,9 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,
const struct bpf_insn *insn)
{
- return env->bypass_spec_v1 || BPF_SRC(insn->code) == BPF_K;
+ return env->bypass_spec_v1 ||
+ BPF_SRC(insn->code) == BPF_K ||
+ cur_aux(env)->nospec;
}
static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux,
@@ -19514,13 +19528,34 @@ static int do_check(struct bpf_verifier_env *env)
sanitize_mark_insn_seen(env);
prev_insn_idx = env->insn_idx;
+ /* Reduce verification complexity by stopping speculative path
+ * verification when a nospec is encountered.
+ */
+ if (state->speculative && cur_aux(env)->nospec)
+ goto process_bpf_exit;
+
err = do_check_insn(env, insn, pop_log, &do_print_state, regs, state,
&prev_insn_idx);
- if (err < 0) {
+ if (state->speculative && error_recoverable_with_nospec(err)) {
+ /* Prevent this speculative path from ever reaching the
+ * insn that would have been unsafe to execute.
+ */
+ cur_aux(env)->nospec = true;
+ /* If it was an ADD/SUB insn, potentially remove any
+ * markings for alu sanitization.
+ */
+ cur_aux(env)->alu_state = 0;
+ goto process_bpf_exit;
+ } else if (err < 0) {
return err;
} else if (err == INSN_IDX_MODIFIED) {
continue;
} else if (err == PROCESS_BPF_EXIT) {
+ goto process_bpf_exit;
+ }
+ WARN_ON_ONCE(err);
+
+ if (state->speculative && cur_aux(env)->nospec_result) {
process_bpf_exit:
mark_verifier_state_scratched(env);
update_branch_counts(env, env->cur_state);
@@ -19539,7 +19574,6 @@ static int do_check(struct bpf_verifier_env *env)
continue;
}
}
- WARN_ON_ONCE(err);
env->insn_idx++;
}
@@ -20670,6 +20704,29 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
bpf_convert_ctx_access_t convert_ctx_access;
u8 mode;
+ if (env->insn_aux_data[i + delta].nospec) {
+ WARN_ON_ONCE(env->insn_aux_data[i + delta].alu_state);
+ struct bpf_insn patch[] = {
+ BPF_ST_NOSPEC(),
+ *insn,
+ };
+
+ cnt = ARRAY_SIZE(patch);
+ new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
+ if (!new_prog)
+ return -ENOMEM;
+
+ delta += cnt - 1;
+ env->prog = new_prog;
+ insn = new_prog->insnsi + i + delta;
+ /* This can not be easily merged with the
+ * nospec_result-case, because an insn may require a
+ * nospec before and after itself. Therefore also do not
+ * 'continue' here but potentially apply further
+ * patching to insn. *insn should equal patch[1] now.
+ */
+ }
+
if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
@@ -20720,6 +20777,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
if (type == BPF_WRITE &&
env->insn_aux_data[i + delta].nospec_result) {
+ /* nospec_result is only used to mitigate Spectre v4 and
+ * to limit verification-time for Spectre v1.
+ */
struct bpf_insn patch[] = {
*insn,
BPF_ST_NOSPEC(),
@@ -85,7 +85,7 @@ l0_%=: r0 = r0; \
SEC("socket")
__description("check known subreg with unknown reg")
-__success __failure_unpriv __msg_unpriv("R1 !read_ok")
+__success __success_unpriv
__retval(0)
__naked void known_subreg_with_unknown_reg(void)
{
@@ -96,6 +96,7 @@ __naked void known_subreg_with_unknown_reg(void)
r0 &= 0xFFFF1234; \
/* Upper bits are unknown but AND above masks out 1 zero'ing lower bits */\
if w0 < 1 goto l0_%=; \
+ /* unpriv: nospec (inserted to prevent `R1 !read_ok'`) */\
r1 = *(u32*)(r1 + 512); \
l0_%=: r0 = 0; \
exit; \
@@ -620,7 +620,7 @@ l1_%=: exit; \
SEC("socket")
__description("bounds check mixed 32bit and 64bit arithmetic. test1")
-__success __failure_unpriv __msg_unpriv("R0 invalid mem access 'scalar'")
+__success __success_unpriv
__retval(0)
__naked void _32bit_and_64bit_arithmetic_test1(void)
{
@@ -636,6 +636,7 @@ __naked void _32bit_and_64bit_arithmetic_test1(void)
if w1 > 2 goto l0_%=; \
goto l1_%=; \
l0_%=: /* invalid ldx if bounds are lost above */ \
+ /* unpriv: nospec (inserted to prevent `R0 invalid mem access 'scalar'`) */\
r0 = *(u64*)(r0 - 1); \
l1_%=: exit; \
" ::: __clobber_all);
@@ -643,7 +644,7 @@ l1_%=: exit; \
SEC("socket")
__description("bounds check mixed 32bit and 64bit arithmetic. test2")
-__success __failure_unpriv __msg_unpriv("R0 invalid mem access 'scalar'")
+__success __success_unpriv
__retval(0)
__naked void _32bit_and_64bit_arithmetic_test2(void)
{
@@ -660,6 +661,7 @@ __naked void _32bit_and_64bit_arithmetic_test2(void)
if r1 > r2 goto l0_%=; \
goto l1_%=; \
l0_%=: /* invalid ldx if bounds are lost above */ \
+ /* unpriv: nospec (inserted to prevent `R0 invalid mem access 'scalar'`) */\
r0 = *(u64*)(r0 - 1); \
l1_%=: exit; \
" ::: __clobber_all);
@@ -691,8 +693,7 @@ l0_%=: r0 = 0; \
SEC("socket")
__description("bounds check for reg = 0, reg xor 1")
-__success __failure_unpriv
-__msg_unpriv("R0 min value is outside of the allowed memory range")
+__success __success_unpriv
__retval(0)
__naked void reg_0_reg_xor_1(void)
{
@@ -708,6 +709,7 @@ __naked void reg_0_reg_xor_1(void)
l0_%=: r1 = 0; \
r1 ^= 1; \
if r1 != 0 goto l1_%=; \
+ /* unpriv: nospec (inserted to prevent `R0 min value is outside of the allowed memory range`) */\
r0 = *(u64*)(r0 + 8); \
l1_%=: r0 = 0; \
exit; \
@@ -719,8 +721,7 @@ l1_%=: r0 = 0; \
SEC("socket")
__description("bounds check for reg32 = 0, reg32 xor 1")
-__success __failure_unpriv
-__msg_unpriv("R0 min value is outside of the allowed memory range")
+__success __success_unpriv
__retval(0)
__naked void reg32_0_reg32_xor_1(void)
{
@@ -736,6 +737,7 @@ __naked void reg32_0_reg32_xor_1(void)
l0_%=: w1 = 0; \
w1 ^= 1; \
if w1 != 0 goto l1_%=; \
+ /* unpriv: nospec (inserted to prevent `R0 min value is outside of the allowed memory range`) */\
r0 = *(u64*)(r0 + 8); \
l1_%=: r0 = 0; \
exit; \
@@ -747,8 +749,7 @@ l1_%=: r0 = 0; \
SEC("socket")
__description("bounds check for reg = 2, reg xor 3")
-__success __failure_unpriv
-__msg_unpriv("R0 min value is outside of the allowed memory range")
+__success __success_unpriv
__retval(0)
__naked void reg_2_reg_xor_3(void)
{
@@ -764,6 +765,7 @@ __naked void reg_2_reg_xor_3(void)
l0_%=: r1 = 2; \
r1 ^= 3; \
if r1 > 0 goto l1_%=; \
+ /* unpriv: nospec (inserted to prevent `R0 min value is outside of the allowed memory range`) */\
r0 = *(u64*)(r0 + 8); \
l1_%=: r0 = 0; \
exit; \
@@ -829,8 +831,7 @@ l1_%=: r0 = 0; \
SEC("socket")
__description("bounds check for reg > 0, reg xor 3")
-__success __failure_unpriv
-__msg_unpriv("R0 min value is outside of the allowed memory range")
+__success __success_unpriv
__retval(0)
__naked void reg_0_reg_xor_3(void)
{
@@ -843,7 +844,8 @@ __naked void reg_0_reg_xor_3(void)
call %[bpf_map_lookup_elem]; \
if r0 != 0 goto l0_%=; \
exit; \
-l0_%=: r1 = *(u64*)(r0 + 0); \
+l0_%=: /* unpriv: nospec (inserted to prevent `R0 min value is outside of the allowed memory range`) */\
+ r1 = *(u64*)(r0 + 0); \
if r1 <= 0 goto l1_%=; \
r1 ^= 3; \
if r1 >= 0 goto l1_%=; \
@@ -858,8 +860,7 @@ l1_%=: r0 = 0; \
SEC("socket")
__description("bounds check for reg32 > 0, reg32 xor 3")
-__success __failure_unpriv
-__msg_unpriv("R0 min value is outside of the allowed memory range")
+__success __success_unpriv
__retval(0)
__naked void reg32_0_reg32_xor_3(void)
{
@@ -872,7 +873,8 @@ __naked void reg32_0_reg32_xor_3(void)
call %[bpf_map_lookup_elem]; \
if r0 != 0 goto l0_%=; \
exit; \
-l0_%=: r1 = *(u64*)(r0 + 0); \
+l0_%=: /* unpriv: nospec (inserted to prevent `R0 min value is outside of the allowed memory range`) */\
+ r1 = *(u64*)(r0 + 0); \
if w1 <= 0 goto l1_%=; \
w1 ^= 3; \
if w1 >= 0 goto l1_%=; \
@@ -245,7 +245,7 @@ l0_%=: \
SEC("socket")
__description("MOV32SX, S8, var_off not u32_max, positive after s8 extension")
__success __retval(0)
-__failure_unpriv __msg_unpriv("frame pointer is read only")
+__success_unpriv
__naked void mov64sx_s32_varoff_2(void)
{
asm volatile (" \
@@ -257,6 +257,7 @@ __naked void mov64sx_s32_varoff_2(void)
w0 = 0; \
exit; \
l0_%=: \
+ /* nospec (inserted to prevent `frame pointer is read only`) */\
r10 = 1; \
exit; \
" :
@@ -267,7 +268,7 @@ l0_%=: \
SEC("socket")
__description("MOV32SX, S8, var_off not u32_max, negative after s8 extension")
__success __retval(0)
-__failure_unpriv __msg_unpriv("frame pointer is read only")
+__success_unpriv
__naked void mov64sx_s32_varoff_3(void)
{
asm volatile (" \
@@ -280,6 +281,7 @@ __naked void mov64sx_s32_varoff_3(void)
w0 = 0; \
exit; \
l0_%=: \
+ /* nospec (inserted to prevent `frame pointer is read only`) */\
r10 = 1; \
exit; \
" :
@@ -572,7 +572,7 @@ l0_%=: exit; \
SEC("socket")
__description("alu32: mov u32 const")
-__success __failure_unpriv __msg_unpriv("R7 invalid mem access 'scalar'")
+__success __success_unpriv
__retval(0)
__naked void alu32_mov_u32_const(void)
{
@@ -581,6 +581,7 @@ __naked void alu32_mov_u32_const(void)
w7 &= 1; \
w0 = w7; \
if r0 == 0 goto l0_%=; \
+ /* unpriv: nospec (inserted to prevent `R7 invalid mem access 'scalar'`) */\
r0 = *(u64*)(r7 + 0); \
l0_%=: exit; \
" ::: __clobber_all);
@@ -398,7 +398,8 @@ l2_%=: r0 = 1; \
SEC("socket")
__description("map access: mixing value pointer and scalar, 1")
-__success __failure_unpriv __msg_unpriv("R2 pointer comparison prohibited")
+__success __failure_unpriv
+__msg_unpriv("R2 tried to add from different maps, paths or scalars, pointer arithmetic with it prohibited for !root")
__retval(0)
__naked void value_pointer_and_scalar_1(void)
{
@@ -433,6 +434,7 @@ l2_%=: /* common instruction */ \
l3_%=: /* branch B */ \
r0 = 0x13371337; \
/* verifier follows fall-through */ \
+ /* unpriv: nospec (inserted to prevent `R2 pointer comparison prohibited`) */\
if r2 != 0x100000 goto l4_%=; \
r0 = 0; \
exit; \
@@ -450,7 +452,8 @@ l4_%=: /* fake-dead code; targeted from branch A to \
SEC("socket")
__description("map access: mixing value pointer and scalar, 2")
-__success __failure_unpriv __msg_unpriv("R0 invalid mem access 'scalar'")
+__success __failure_unpriv
+__msg_unpriv("R2 tried to add from different maps, paths or scalars, pointer arithmetic with it prohibited for !root")
__retval(0)
__naked void value_pointer_and_scalar_2(void)
{
@@ -466,6 +469,7 @@ __naked void value_pointer_and_scalar_2(void)
if r0 != 0 goto l0_%=; \
exit; \
l0_%=: /* load some number from the map into r1 */ \
+ /* unpriv: nospec (inserted to prevent `R0 invalid mem access 'scalar'`) */\
r1 = *(u8*)(r0 + 0); \
/* depending on r1, branch: */ \
if r1 == 0 goto l1_%=; \
@@ -1296,11 +1300,13 @@ l0_%=: r0 = 1; \
SEC("socket")
__description("map access: value_ptr -= unknown scalar, 2")
-__success __failure_unpriv
-__msg_unpriv("R0 pointer arithmetic of map value goes out of range")
+__success __success_unpriv
__retval(1)
__naked void value_ptr_unknown_scalar_2_2(void)
{
+ /* unpriv: nospec inserted by verifier to mitigate 'R0 pointer
+ * arithmetic of map value goes out of range'.
+ */
asm volatile (" \
r1 = 0; \
*(u64*)(r10 - 8) = r1; \
@@ -2,14 +2,13 @@
"dead code: start",
.insns = {
BPF_JMP_IMM(BPF_JA, 0, 0, 2),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_JMP_IMM(BPF_JA, 0, 0, 2),
BPF_MOV64_IMM(BPF_REG_0, 7),
BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, -4),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 7,
},
@@ -84,11 +84,10 @@
BPF_JMP32_IMM(BPF_JSET, BPF_REG_7, 0x10, 1),
BPF_EXIT_INSN(),
BPF_JMP32_IMM(BPF_JGE, BPF_REG_7, 0x10, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
{
@@ -149,11 +148,10 @@
BPF_JMP32_IMM(BPF_JEQ, BPF_REG_7, 0x10, 1),
BPF_EXIT_INSN(),
BPF_JMP32_IMM(BPF_JSGE, BPF_REG_7, 0xf, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
{
@@ -214,11 +212,10 @@
BPF_JMP32_IMM(BPF_JNE, BPF_REG_7, 0x10, 1),
BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0x10, 1),
BPF_EXIT_INSN(),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
{
@@ -283,11 +280,10 @@
BPF_JMP32_REG(BPF_JGE, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP32_IMM(BPF_JGE, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -354,11 +350,10 @@
BPF_JMP32_REG(BPF_JGT, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JGT, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -425,11 +420,10 @@
BPF_JMP32_REG(BPF_JLE, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP32_IMM(BPF_JLE, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -496,11 +490,10 @@
BPF_JMP32_REG(BPF_JLT, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -567,11 +560,10 @@
BPF_JMP32_REG(BPF_JSGE, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -638,11 +630,10 @@
BPF_JMP32_REG(BPF_JSGT, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JSGT, BPF_REG_7, -2, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -709,11 +700,10 @@
BPF_JMP32_REG(BPF_JSLE, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JSLE, BPF_REG_7, 0x7ffffff0, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -780,11 +770,10 @@
BPF_JMP32_REG(BPF_JSLT, BPF_REG_7, BPF_REG_8, 1),
BPF_EXIT_INSN(),
BPF_JMP32_IMM(BPF_JSLT, BPF_REG_7, -1, 1),
+ /* unpriv: nospec (inserted to prevent "R0 invalid mem access 'scalar'") */
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R0 invalid mem access 'scalar'",
- .result_unpriv = REJECT,
.result = ACCEPT,
.retval = 2,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
@@ -78,12 +78,11 @@
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_JMP_IMM(BPF_JSET, BPF_REG_0, 1, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.retval = 1,
.result = ACCEPT,
},
@@ -136,13 +135,12 @@
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_get_prandom_u32),
BPF_ALU64_IMM(BPF_OR, BPF_REG_0, 2),
BPF_JMP_IMM(BPF_JSET, BPF_REG_0, 3, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
{
@@ -154,16 +152,16 @@
BPF_ALU64_IMM(BPF_AND, BPF_REG_1, 0xff),
BPF_JMP_IMM(BPF_JSET, BPF_REG_1, 0xf0, 3),
BPF_JMP_IMM(BPF_JLT, BPF_REG_1, 0x10, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JSET, BPF_REG_1, 0x10, 1),
BPF_EXIT_INSN(),
BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 0x10, 1),
+ /* unpriv: nospec (inserted to prevent "R9 !read_ok") */
BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
- .errstr_unpriv = "R9 !read_ok",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
This implements the core of the series and causes the verifier to fall back to mitigating Spectre v1 using speculation barriers. The approach was presented at LPC'24 [1] and RAID'24 [2]. This has the unfortunate consequence that Spectre v1 mitigations now only support architectures which implement BPF_NOSPEC. Before this commit, Spectre v1 mitigations prevented exploits by rejecting the programs on all architectures. Because some JITs do not implement BPF_NOSPEC, this patch therefore may regress unpriv BPF's security to a limited extent: * The regression is limited to systems vulnerable to Spectre v1, have unprivileged BPF enabled, and do NOT emit insns for BPF_NOSPEC. The latter is not the case for x86 64- and 32-bit, arm64, and powerpc 64-bit and they are therefore not affected by the regression. According to commit a6f6a95f2580 ("LoongArch, bpf: Fix jit to skip speculation barrier opcode"), LoongArch is not vulnerable to Spectre v1 and therefore also not affected by the regression. * To the best of my knowledge this regression may therefore only affect MIPS. This is deemed acceptable because unpriv BPF is still disabled there by default. As stated in a previous commit, BPF_NOSPEC could be implemented for MIPS based on GCC's speculation_barrier implementation. * It is unclear which other architectures (besides x86 64- and 32-bit, ARM64, PowerPC 64-bit, LoongArch, and MIPS) supported by the kernel are vulnerable to Spectre v1. Also, it is not clear if barriers are available on these architectures. Implementing BPF_NOSPEC on these architectures therefore is non-trivial. Searching GCC and the kernel for speculation barrier implementations for these architectures yielded no result. * If any of those regressed systems is also vulnerable to Spectre v4, the system was already vulnerable to Spectre v4 attacks based on unpriv BPF before this patch and the impact is therefore further limited. As an alternative to regressing security, one could still reject programs if the architecture does not emit BPF_NOSPEC (e.g., by removing the empty BPF_NOSPEC-case from all JITs except for LoongArch where it appears justified). However, this will cause rejections on these archs that are likely unfounded in the vast majority of cases. In the tests, some are now successful where we previously had a false-positive (i.e., rejection). Change them to reflect where the nospec should be inserted (as comment) and modify the error message if the nospec is able to mitigate a problem that previously shadowed another problem. Briefly went through all the occurrences of EPERM, EINVAL, and EACCESS in the verifier in order to validate that catching them like this makes sense. [1] https://lpc.events/event/18/contributions/1954/ ("Mitigating Spectre-PHT using Speculation Barriers in Linux eBPF") [2] https://arxiv.org/pdf/2405.00078 ("VeriFence: Lightweight and Precise Spectre Defenses for Untrusted Linux Kernel Extensions") Signed-off-by: Luis Gerhorst <luis.gerhorst@fau.de> Acked-by: Henriette Herzog <henriette.herzog@rub.de> Cc: Maximilian Ott <ott@cs.fau.de> Cc: Milan Stephan <milan.stephan@fau.de> --- include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 68 +++++++++++++++++-- .../selftests/bpf/progs/verifier_and.c | 3 +- .../selftests/bpf/progs/verifier_bounds.c | 30 ++++---- .../selftests/bpf/progs/verifier_movsx.c | 6 +- .../selftests/bpf/progs/verifier_unpriv.c | 3 +- .../bpf/progs/verifier_value_ptr_arith.c | 14 ++-- .../selftests/bpf/verifier/dead_code.c | 3 +- tools/testing/selftests/bpf/verifier/jmp32.c | 33 +++------ tools/testing/selftests/bpf/verifier/jset.c | 10 ++- 10 files changed, 115 insertions(+), 56 deletions(-)