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    Subject[PATCH 5.13 232/266] seq_buf: Fix overflow in seq_buf_putmem_hex()
    Date
    From: Yun Zhou <yun.zhou@windriver.com>

    commit d3b16034a24a112bb83aeb669ac5b9b01f744bb7 upstream.

    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.

    Link: https://lore.kernel.org/lkml/20210625122453.5e2fe304@oasis.local.home/
    Link: https://lkml.kernel.org/r/20210626032156.47889-1-yun.zhou@windriver.com

    Cc: stable@vger.kernel.org
    Fixes: 5e3ca0ec76fce ("ftrace: introduce the "hex" output method")
    Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    lib/seq_buf.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/lib/seq_buf.c
    +++ b/lib/seq_buf.c
    @@ -229,8 +229,10 @@ int seq_buf_putmem_hex(struct seq_buf *s

    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

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