linux-kernel - [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map

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Date:   Fri, 11 Nov 2022 07:56:20 -0500
From:   Xu Kuohai <xukuohai@...weicloud.com>
To:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

From: Xu Kuohai <xukuohai@...wei.com>

Function __copy_map_value and zero_map_value miscalculated copy offset,
resulting in possible copy of unwanted data to user or kernel.

Fix it.

Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with special fields")
Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
Signed-off-by: Xu Kuohai <xukuohai@...wei.com>
---
 include/linux/bpf.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 74c6f449d81e..c1bd1bd10506 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -315,7 +315,7 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
 		u32 next_off = map->off_arr->field_off[i];
 
 		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		curr_off = next_off + map->off_arr->field_sz[i];
 	}
 	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
 }
@@ -344,7 +344,7 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
 		u32 next_off = map->off_arr->field_off[i];
 
 		memset(dst + curr_off, 0, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		curr_off = next_off + map->off_arr->field_sz[i];
 	}
 	memset(dst + curr_off, 0, map->value_size - curr_off);
 }
-- 
2.30.2