| Message ID | 20210626032156.47889-1-yun.zhou@windriver.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] seq_buf: fix overflow in seq_buf_putmem_hex() | expand |
diff --git a/lib/seq_buf.c b/lib/seq_buf.c index 6aabb609dd87..223fbc3bb958 100644 --- a/lib/seq_buf.c +++ b/lib/seq_buf.c @@ -228,8 +228,10 @@ int seq_buf_putmem_hex(struct seq_buf *s, const void *mem, WARN_ON(s->size == 0); + BUILD_BUG_ON(MAX_MEMHEX_BYTES * 2 >= HEX_CHARS); + 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++) { #else
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 exists in the original code (commit 5e3ca0ec76fce 'ftrace: introduce the "hex" output method'). Although its original design did not support more than 8 bytes, the only check on length seems to have mistaken the comparison object, 'len' should compare to 'HEX_CHARS/2'. BUG_ON(len >= HEX_CHARS); Signed-off-by: Yun Zhou <yun.zhou@windriver.com> --- lib/seq_buf.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)