Commit e9730744 authored by Daniel Thompson's avatar Daniel Thompson
Browse files

kdb: Fix buffer overflow during tab-complete 



Currently, when the user attempts symbol completion with the Tab key, kdb
will use strncpy() to insert the completed symbol into the command buffer.
Unfortunately it passes the size of the source buffer rather than the
destination to strncpy() with predictably horrible results. Most obviously
if the command buffer is already full but cp, the cursor position, is in
the middle of the buffer, then we will write past the end of the supplied
buffer.

Fix this by replacing the dubious strncpy() calls with memmove()/memcpy()
calls plus explicit boundary checks to make sure we have enough space
before we start moving characters around.

Reported-by: default avatarJustin Stitt <justinstitt@google.com>
Closes: https://lore.kernel.org/all/CAFhGd8qESuuifuHsNjFPR-Va3P80bxrw+LqvC8deA8GziUJLpw@mail.gmail.com/


Cc: stable@vger.kernel.org
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarJustin Stitt <justinstitt@google.com>
Tested-by: default avatarJustin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-1-f236dbe9828d@linaro.org


Signed-off-by: default avatarDaniel Thompson <daniel.thompson@linaro.org>
parent 5b6d8ef6

kernel/debug/kdb/kdb_io.c

+13 −8
Original line number Diff line number Diff line
@@ -367,14 +367,19 @@ static char *kdb_read(char *buffer, size_t bufsize) 
			kdb_printf(kdb_prompt_str);

			kdb_printf("%s", buffer);

		} else if (tab != 2 && count > 0) {

			len_tmp = strlen(p_tmp);

			strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);

			len_tmp = strlen(p_tmp);

			strncpy(cp, p_tmp+len, len_tmp-len + 1);

			len = len_tmp - len;

			/* How many new characters do we want from tmpbuffer? */

			len_tmp = strlen(p_tmp) - len;

			if (lastchar + len_tmp >= bufend)

				len_tmp = bufend - lastchar;



			if (len_tmp) {

				/* + 1 ensures the '\0' is memmove'd */

				memmove(cp+len_tmp, cp, (lastchar-cp) + 1);

				memcpy(cp, p_tmp+len, len_tmp);

				kdb_printf("%s", cp);

			cp += len;

			lastchar += len;

				cp += len_tmp;

				lastchar += len_tmp;

			}

		}

		kdb_nextline = 1; /* reset output line number */

		break;