seq_buf: Fix overflow in seq_buf_putmem_hex()

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/[email protected]/ Link: https://lkml.kernel.org/r/[email protected] Cc: [email protected] Fixes: 5e3ca0e ("ftrace: introduce the "hex" output method") Signed-off-by: Yun Zhou <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
gardiol · Jul 20, 2021 · 50b5146 · 50b5146
1 parent 5802339
commit 50b5146
Showing 1 changed file with 3 additions and 1 deletion.
diff --git 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