linux-kernel - [PATCH bpf-next v2] bpf: check flags in 'bpf_ringbuf_discard()' and 'bpf_ringbuf

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Message-Id: <20210330223748.399563-1-pctammela@mojatatu.com>
Date:   Tue, 30 Mar 2021 19:37:46 -0300
From:   Pedro Tammela <pctammela@...il.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Joe Stringer <joe@...ium.io>,
        Quentin Monnet <quentin@...valent.com>,
        netdev@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        bpf@...r.kernel.org (open list:BPF (Safe dynamic programs and tools)),
        linux-kernel@...r.kernel.org (open list)
Cc:     Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH bpf-next v2] bpf: check flags in 'bpf_ringbuf_discard()' and 'bpf_ringbuf_submit()'

The current code only checks flags in 'bpf_ringbuf_output()'.

Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
---
 include/uapi/linux/bpf.h       |  8 ++++----
 kernel/bpf/ringbuf.c           | 13 +++++++++++--
 tools/include/uapi/linux/bpf.h |  8 ++++----
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 100cb2e4c104..38b0b15f99f0 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4073,7 +4073,7 @@ union bpf_attr {
  * 		Valid pointer with *size* bytes of memory available; NULL,
  * 		otherwise.
  *
- * void bpf_ringbuf_submit(void *data, u64 flags)
+ * long bpf_ringbuf_submit(void *data, u64 flags)
  * 	Description
  * 		Submit reserved ring buffer sample, pointed to by *data*.
  * 		If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
@@ -4083,9 +4083,9 @@ union bpf_attr {
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
  * 	Return
- * 		Nothing. Always succeeds.
+ * 		0 on success, or a negative error in case of failure.
  *
- * void bpf_ringbuf_discard(void *data, u64 flags)
+ * long bpf_ringbuf_discard(void *data, u64 flags)
  * 	Description
  * 		Discard reserved ring buffer sample, pointed to by *data*.
  * 		If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
@@ -4095,7 +4095,7 @@ union bpf_attr {
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
  * 	Return
- * 		Nothing. Always succeeds.
+ * 		0 on success, or a negative error in case of failure.
  *
  * u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
  *	Description
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index f25b719ac786..f76dafe2427e 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -397,26 +397,35 @@ static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
 
 BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
 {
+	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
+		return -EINVAL;
+
 	bpf_ringbuf_commit(sample, flags, false /* discard */);
+
 	return 0;
 }
 
 const struct bpf_func_proto bpf_ringbuf_submit_proto = {
 	.func		= bpf_ringbuf_submit,
-	.ret_type	= RET_VOID,
+	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM,
 	.arg2_type	= ARG_ANYTHING,
 };
 
 BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
 {
+
+	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
+		return -EINVAL;
+
 	bpf_ringbuf_commit(sample, flags, true /* discard */);
+
 	return 0;
 }
 
 const struct bpf_func_proto bpf_ringbuf_discard_proto = {
 	.func		= bpf_ringbuf_discard,
-	.ret_type	= RET_VOID,
+	.ret_type	= RET_INTEGER,
 	.arg1_type	= ARG_PTR_TO_ALLOC_MEM,
 	.arg2_type	= ARG_ANYTHING,
 };
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 3d6d324184c0..a32eefb786f9 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4073,7 +4073,7 @@ union bpf_attr {
  * 		Valid pointer with *size* bytes of memory available; NULL,
  * 		otherwise.
  *
- * void bpf_ringbuf_submit(void *data, u64 flags)
+ * long bpf_ringbuf_submit(void *data, u64 flags)
  * 	Description
  * 		Submit reserved ring buffer sample, pointed to by *data*.
  * 		If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
@@ -4083,9 +4083,9 @@ union bpf_attr {
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
  * 	Return
- * 		Nothing. Always succeeds.
+ * 		0 on success, or a negative error in case of failure.
  *
- * void bpf_ringbuf_discard(void *data, u64 flags)
+ * long bpf_ringbuf_discard(void *data, u64 flags)
  * 	Description
  * 		Discard reserved ring buffer sample, pointed to by *data*.
  * 		If **BPF_RB_NO_WAKEUP** is specified in *flags*, no notification
@@ -4095,7 +4095,7 @@ union bpf_attr {
  * 		If **BPF_RB_FORCE_WAKEUP** is specified in *flags*, notification
  * 		of new data availability is sent unconditionally.
  * 	Return
- * 		Nothing. Always succeeds.
+ * 		0 on success, or a negative error in case of failure.
  *
  * u64 bpf_ringbuf_query(void *ringbuf, u64 flags)
  *	Description
-- 
2.25.1