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Date: Fri, 25 Jun 2021 23:53:47 +0800
From: Yun Zhou <yun.zhou@...driver.com>
To: <rostedt@...dmis.org>
CC: <linux-kernel@...r.kernel.org>, <kernel-hardening@...ts.openwall.com>,
<ying.xue@...driver.com>, <zhiquan.li@...driver.com>
Subject: [PATCH 1/2] seq_buf: fix overflow when length is bigger than 8
There's two variables being increased in that loop (i and j), and i
follows the raw data, and j follows what is being written into the buffer.
We should compare 'i' to MAX_MEMHEX_BYTES or compare 'j' to HEX_CHARS.
Otherwise, if 'j' goes bigger than HEX_CHARS, it will overflow the
destination buffer.
This bug was introduced by commit 6d2289f3faa71dcc ("tracing: Make
trace_seq_putmem_hex() more robust")
Signed-off-by: Yun Zhou <yun.zhou@...driver.com>
---
lib/seq_buf.c | 29 +++++++++++------------------
1 file changed, 11 insertions(+), 18 deletions(-)
diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 6aabb609dd87..aa2f666e584e 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -210,7 +210,8 @@ int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
* seq_buf_putmem_hex - write raw memory into the buffer in ASCII hex
* @s: seq_buf descriptor
* @mem: The raw memory to write its hex ASCII representation of
- * @len: The length of the raw memory to copy (in bytes)
+ * @len: The length of the raw memory to copy (in bytes).
+ * It can be not larger than 8.
*
* This is similar to seq_buf_putmem() except instead of just copying the
* raw memory into the buffer it writes its ASCII representation of it
@@ -228,27 +229,19 @@ int seq_buf_putmem_hex(struct seq_buf *s, const void *mem,
WARN_ON(s->size == 0);
- while (len) {
- start_len = min(len, HEX_CHARS - 1);
+ start_len = min(len, MAX_MEMHEX_BYTES);
#ifdef __BIG_ENDIAN
- for (i = 0, j = 0; i < start_len; i++) {
+ for (i = 0, j = 0; i < start_len; i++) {
#else
- for (i = start_len-1, j = 0; i >= 0; i--) {
+ for (i = start_len-1, j = 0; i >= 0; i--) {
#endif
- hex[j++] = hex_asc_hi(data[i]);
- hex[j++] = hex_asc_lo(data[i]);
- }
- if (WARN_ON_ONCE(j == 0 || j/2 > len))
- break;
-
- /* j increments twice per loop */
- len -= j / 2;
- hex[j++] = ' ';
-
- seq_buf_putmem(s, hex, j);
- if (seq_buf_has_overflowed(s))
- return -1;
+ hex[j++] = hex_asc_hi(data[i]);
+ hex[j++] = hex_asc_lo(data[i]);
}
+
+ seq_buf_putmem(s, hex, j);
+ if (seq_buf_has_overflowed(s))
+ return -1;
return 0;
}
--
2.26.1
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