* [PATCH bpf-next 1/3] bpf: Allow narrow loads with offset > 0
2018-11-07 1:23 [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Andrey Ignatov
@ 2018-11-07 1:23 ` Andrey Ignatov
2018-11-07 1:23 ` [PATCH bpf-next 2/3] selftests/bpf: Test narrow loads with off > 0 in test_verifier Andrey Ignatov
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Ignatov @ 2018-11-07 1:23 UTC (permalink / raw)
To: netdev; +Cc: Andrey Ignatov, ast, daniel, yhs, kernel-team
Currently BPF verifier allows narrow loads for a context field only with
offset zero. E.g. if there is a __u32 field then only the following
loads are permitted:
* off=0, size=1 (narrow);
* off=0, size=2 (narrow);
* off=0, size=4 (full).
On the other hand LLVM can generate a load with offset different than
zero that make sense from program logic point of view, but verifier
doesn't accept it.
E.g. tools/testing/selftests/bpf/sendmsg4_prog.c has code:
#define DST_IP4 0xC0A801FEU /* 192.168.1.254 */
...
if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
where ctx is struct bpf_sock_addr.
Some versions of LLVM can produce the following byte code for it:
8: 71 12 07 00 00 00 00 00 r2 = *(u8 *)(r1 + 7)
9: 67 02 00 00 18 00 00 00 r2 <<= 24
10: 18 03 00 00 00 00 00 fe 00 00 00 00 00 00 00 00 r3 = 4261412864 ll
12: 5d 32 07 00 00 00 00 00 if r2 != r3 goto +7 <LBB0_6>
where `*(u8 *)(r1 + 7)` means narrow load for ctx->user_ip4 with size=1
and offset=3 (7 - sizeof(ctx->user_family) = 3). This load is currently
rejected by verifier.
Verifier code that rejects such loads is in bpf_ctx_narrow_access_ok()
what means any is_valid_access implementation, that uses the function,
works this way, e.g. bpf_skb_is_valid_access() for __sk_buff or
sock_addr_is_valid_access() for bpf_sock_addr.
The patch makes such loads supported. Offset can be in [0; size_default)
but has to be multiple of load size. E.g. for __u32 field the following
loads are supported now:
* off=0, size=1 (narrow);
* off=1, size=1 (narrow);
* off=2, size=1 (narrow);
* off=3, size=1 (narrow);
* off=0, size=2 (narrow);
* off=2, size=2 (narrow);
* off=0, size=4 (full).
Reported-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
include/linux/filter.h | 16 +---------------
kernel/bpf/verifier.c | 19 +++++++++++++++----
2 files changed, 16 insertions(+), 19 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index de629b706d1d..cc17f5f32fbb 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -668,24 +668,10 @@ static inline u32 bpf_ctx_off_adjust_machine(u32 size)
return size;
}
-static inline bool bpf_ctx_narrow_align_ok(u32 off, u32 size_access,
- u32 size_default)
-{
- size_default = bpf_ctx_off_adjust_machine(size_default);
- size_access = bpf_ctx_off_adjust_machine(size_access);
-
-#ifdef __LITTLE_ENDIAN
- return (off & (size_default - 1)) == 0;
-#else
- return (off & (size_default - 1)) + size_access == size_default;
-#endif
-}
-
static inline bool
bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default)
{
- return bpf_ctx_narrow_align_ok(off, size, size_default) &&
- size <= size_default && (size & (size - 1)) == 0;
+ return size <= size_default && (size & (size - 1)) == 0;
}
#define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1971ca325fb4..fa592502568e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5803,9 +5803,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
* we will apply proper mask to the result.
*/
is_narrower_load = size < ctx_field_size;
+ u32 size_default = bpf_ctx_off_adjust_machine(ctx_field_size);
+ u32 off = insn->off;
if (is_narrower_load) {
- u32 size_default = bpf_ctx_off_adjust_machine(ctx_field_size);
- u32 off = insn->off;
u8 size_code;
if (type == BPF_WRITE) {
@@ -5833,12 +5833,23 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
}
if (is_narrower_load && size < target_size) {
- if (ctx_field_size <= 4)
+ u8 shift = (off & (size_default - 1)) * 8;
+
+ if (ctx_field_size <= 4) {
+ if (shift)
+ insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH,
+ insn->dst_reg,
+ shift);
insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
- else
+ } else {
+ if (shift)
+ insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH,
+ insn->dst_reg,
+ shift);
insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
(1 << size * 8) - 1);
+ }
}
new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH bpf-next 2/3] selftests/bpf: Test narrow loads with off > 0 in test_verifier
2018-11-07 1:23 [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Andrey Ignatov
2018-11-07 1:23 ` [PATCH bpf-next 1/3] " Andrey Ignatov
@ 2018-11-07 1:23 ` Andrey Ignatov
2018-11-07 1:23 ` [PATCH bpf-next 3/3] selftests/bpf: Test narrow loads with off > 0 for bpf_sock_addr Andrey Ignatov
2018-11-10 19:13 ` [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Alexei Starovoitov
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Ignatov @ 2018-11-07 1:23 UTC (permalink / raw)
To: netdev; +Cc: Andrey Ignatov, ast, daniel, yhs, kernel-team
Test the following narrow loads in test_verifier for context __sk_buff:
* off=1, size=1 - ok;
* off=2, size=1 - ok;
* off=3, size=1 - ok;
* off=0, size=2 - ok;
* off=1, size=2 - fail;
* off=0, size=2 - ok;
* off=3, size=2 - fail.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
tools/testing/selftests/bpf/test_verifier.c | 48 ++++++++++++++++-----
1 file changed, 38 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 6f61df62f690..54d16fbdef8b 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -2026,29 +2026,27 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
},
{
- "check skb->hash byte load not permitted 1",
+ "check skb->hash byte load permitted 1",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, hash) + 1),
BPF_EXIT_INSN(),
},
- .errstr = "invalid bpf_context access",
- .result = REJECT,
+ .result = ACCEPT,
},
{
- "check skb->hash byte load not permitted 2",
+ "check skb->hash byte load permitted 2",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, hash) + 2),
BPF_EXIT_INSN(),
},
- .errstr = "invalid bpf_context access",
- .result = REJECT,
+ .result = ACCEPT,
},
{
- "check skb->hash byte load not permitted 3",
+ "check skb->hash byte load permitted 3",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
#if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -2060,8 +2058,7 @@ static struct bpf_test tests[] = {
#endif
BPF_EXIT_INSN(),
},
- .errstr = "invalid bpf_context access",
- .result = REJECT,
+ .result = ACCEPT,
},
{
"check cb access: byte, wrong type",
@@ -2173,7 +2170,7 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
},
{
- "check skb->hash half load not permitted",
+ "check skb->hash half load permitted 2",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
#if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -2182,6 +2179,37 @@ static struct bpf_test tests[] = {
#else
BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, hash)),
+#endif
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ },
+ {
+ "check skb->hash half load not permitted, unaligned 1",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, hash) + 1),
+#else
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, hash) + 3),
+#endif
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid bpf_context access",
+ .result = REJECT,
+ },
+ {
+ "check skb->hash half load not permitted, unaligned 3",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, hash) + 3),
+#else
+ BPF_LDX_MEM(BPF_H, BPF_REG_0, BPF_REG_1,
+ offsetof(struct __sk_buff, hash) + 1),
#endif
BPF_EXIT_INSN(),
},
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH bpf-next 3/3] selftests/bpf: Test narrow loads with off > 0 for bpf_sock_addr
2018-11-07 1:23 [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Andrey Ignatov
2018-11-07 1:23 ` [PATCH bpf-next 1/3] " Andrey Ignatov
2018-11-07 1:23 ` [PATCH bpf-next 2/3] selftests/bpf: Test narrow loads with off > 0 in test_verifier Andrey Ignatov
@ 2018-11-07 1:23 ` Andrey Ignatov
2018-11-10 19:13 ` [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Alexei Starovoitov
3 siblings, 0 replies; 6+ messages in thread
From: Andrey Ignatov @ 2018-11-07 1:23 UTC (permalink / raw)
To: netdev; +Cc: Andrey Ignatov, ast, daniel, yhs, kernel-team
Add more test cases for context bpf_sock_addr to test narrow loads with
offset > 0 for ctx->user_ip4 field (__u32):
* off=1, size=1;
* off=2, size=1;
* off=3, size=1;
* off=2, size=2.
Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
tools/testing/selftests/bpf/test_sock_addr.c | 28 +++++++++++++++++---
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/bpf/test_sock_addr.c b/tools/testing/selftests/bpf/test_sock_addr.c
index aeeb76a54d63..73b7493d4120 100644
--- a/tools/testing/selftests/bpf/test_sock_addr.c
+++ b/tools/testing/selftests/bpf/test_sock_addr.c
@@ -574,24 +574,44 @@ static int bind4_prog_load(const struct sock_addr_test *test)
/* if (sk.family == AF_INET && */
BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
offsetof(struct bpf_sock_addr, family)),
- BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET, 16),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET, 24),
/* (sk.type == SOCK_DGRAM || sk.type == SOCK_STREAM) && */
BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
offsetof(struct bpf_sock_addr, type)),
BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_DGRAM, 1),
BPF_JMP_A(1),
- BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_STREAM, 12),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_STREAM, 20),
/* 1st_byte_of_user_ip4 == expected && */
BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
offsetof(struct bpf_sock_addr, user_ip4)),
- BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[0], 10),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[0], 18),
+
+ /* 2nd_byte_of_user_ip4 == expected && */
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
+ offsetof(struct bpf_sock_addr, user_ip4) + 1),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[1], 16),
+
+ /* 3rd_byte_of_user_ip4 == expected && */
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
+ offsetof(struct bpf_sock_addr, user_ip4) + 2),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[2], 14),
+
+ /* 4th_byte_of_user_ip4 == expected && */
+ BPF_LDX_MEM(BPF_B, BPF_REG_7, BPF_REG_6,
+ offsetof(struct bpf_sock_addr, user_ip4) + 3),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr8[3], 12),
/* 1st_half_of_user_ip4 == expected && */
BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_6,
offsetof(struct bpf_sock_addr, user_ip4)),
- BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr16[0], 8),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr16[0], 10),
+
+ /* 2nd_half_of_user_ip4 == expected && */
+ BPF_LDX_MEM(BPF_H, BPF_REG_7, BPF_REG_6,
+ offsetof(struct bpf_sock_addr, user_ip4) + 2),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_7, ip4.u4_addr16[1], 8),
/* whole_user_ip4 == expected) { */
BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0
2018-11-07 1:23 [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Andrey Ignatov
` (2 preceding siblings ...)
2018-11-07 1:23 ` [PATCH bpf-next 3/3] selftests/bpf: Test narrow loads with off > 0 for bpf_sock_addr Andrey Ignatov
@ 2018-11-10 19:13 ` Alexei Starovoitov
2018-11-10 23:38 ` Alexei Starovoitov
3 siblings, 1 reply; 6+ messages in thread
From: Alexei Starovoitov @ 2018-11-10 19:13 UTC (permalink / raw)
To: Andrey Ignatov; +Cc: netdev, ast, daniel, yhs, kernel-team
On Tue, Nov 06, 2018 at 05:23:25PM -0800, Andrey Ignatov wrote:
> This patch set adds support for narrow loads with offset > 0 to BPF
> verifier.
>
> Patch 1 provides more details and is the main patch in the set.
> Patches 2 and 3 add new test cases to test_verifier and test_sock_addr
> selftests.
Applied, Thanks
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0
2018-11-10 19:13 ` [PATCH bpf-next 0/3] bpf: Allow narrow loads with offset > 0 Alexei Starovoitov
@ 2018-11-10 23:38 ` Alexei Starovoitov
0 siblings, 0 replies; 6+ messages in thread
From: Alexei Starovoitov @ 2018-11-10 23:38 UTC (permalink / raw)
To: Andrey Ignatov
Cc: Network Development, Alexei Starovoitov, Daniel Borkmann,
Yonghong Song, Kernel Team
On Sat, Nov 10, 2018 at 11:13 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Nov 06, 2018 at 05:23:25PM -0800, Andrey Ignatov wrote:
> > This patch set adds support for narrow loads with offset > 0 to BPF
> > verifier.
> >
> > Patch 1 provides more details and is the main patch in the set.
> > Patches 2 and 3 add new test cases to test_verifier and test_sock_addr
> > selftests.
>
> Applied, Thanks
reverted.
please fix compiler warning and respin.
^ permalink raw reply [flat|nested] 6+ messages in thread