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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c24962bbea6sm822160266b.27.2026.08.23.12.32.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Aug 2026 12:32:05 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v1 1/2] bpf: Reject oversized stream read buffers Date: Sun, 23 Aug 2026 21:32:00 +0200 Message-ID: <20260823193202.2389715-2-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260823193202.2389715-1-memxor@gmail.com> References: <20260823193202.2389715-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2102; i=memxor@gmail.com; h=from:subject; bh=0KCANcUaU5iAxqaTywqahr59y0EC3KLBF9VSnRiLjKQ=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIavba37RtjkKsx9N8uzIXTL/1vmWQ4e39Vh/V5M2uP3yH 7vpFMd5HaUsDGJcDLJiiiwl//cxGZ+o/B1ou4wbZg4rE8gQBi5OAZiIxitGhktSv+PlZvvcsIrI Sn38xeUTt3rVumcaO3e6zXZ5d+PDDh6GP7z7+Z+9evnv33Gmt6Ybdx/kShRf8fCp7US7xVvcurg 7VvMDAA== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit BPF_PROG_STREAM_READ_BY_FD exposes stream_buf_len as a u32, but the internal stream reader accepts an int. Values above INT_MAX therefore become negative before bpf_stream_read(), producing negative consumption lengths. The generic usercopy size check prevents the oversized copy, but emits a warning and reports EFAULT for an unchecked argument. Change bpf_prog_stream_read() to accept u32 and reject values that the signed reader cannot represent. Fixes: 5ab154f1463a ("bpf: Introduce BPF standard streams") Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/bpf.h | 2 +- kernel/bpf/stream.c | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index ffa5626411ac..717436698ec3 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -4101,7 +4101,7 @@ void bpf_put_buffers(void); void bpf_prog_stream_init(struct bpf_prog *prog); void bpf_prog_stream_free(struct bpf_prog *prog); -int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, int len); +int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, u32 len); void bpf_stream_stage_init(struct bpf_stream_stage *ss); void bpf_stream_stage_free(struct bpf_stream_stage *ss); __printf(2, 3) diff --git a/kernel/bpf/stream.c b/kernel/bpf/stream.c index 7a5c3ac8676b..2b80a0599865 100644 --- a/kernel/bpf/stream.c +++ b/kernel/bpf/stream.c @@ -203,13 +203,15 @@ static int bpf_stream_read(struct bpf_stream *stream, void __user *buf, int len) return ret ? ret : len - rem_len; } -int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, int len) +int bpf_prog_stream_read(struct bpf_prog *prog, enum bpf_stream_id stream_id, void __user *buf, u32 len) { struct bpf_stream *stream; stream = bpf_stream_get(stream_id, prog->aux); if (!stream) return -ENOENT; + if (len > INT_MAX) + return -EINVAL; return bpf_stream_read(stream, buf, len); } -- 2.53.0