This is a note to let you know that I've just added the patch titled seq_buf: Fix overflow in seq_buf_putmem_hex() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: seq_buf-fix-overflow-in-seq_buf_putmem_hex.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From d3b16034a24a112bb83aeb669ac5b9b01f744bb7 Mon Sep 17 00:00:00 2001 From: Yun Zhou <yun.zhou@xxxxxxxxxxxxx> Date: Sat, 26 Jun 2021 11:21:55 +0800 Subject: seq_buf: Fix overflow in seq_buf_putmem_hex() From: Yun Zhou <yun.zhou@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/20210626032156.47889-1-yun.zhou@xxxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Fixes: 5e3ca0ec76fce ("ftrace: introduce the "hex" output method") Signed-off-by: Yun Zhou <yun.zhou@xxxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- lib/seq_buf.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/lib/seq_buf.c +++ b/lib/seq_buf.c @@ -227,8 +227,10 @@ 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 Patches currently in stable-queue which might be from yun.zhou@xxxxxxxxxxxxx are queue-4.4/seq_buf-fix-overflow-in-seq_buf_putmem_hex.patch queue-4.4/seq_buf-make-trace_seq_putmem_hex-support-data-longer-than-8.patch