From 344409aad2f3ce0aec6a354f9e896db552b70be5 Mon Sep 17 00:00:00 2001 From: Daniel Thompson Date: Wed, 24 Apr 2024 15:03:34 +0100 Subject: [PATCH] kdb: Fix buffer overflow during tab-complete commit e9730744bf3af04cda23799029342aa3cddbc454 upstream. 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: Justin Stitt Closes: https://lore.kernel.org/all/CAFhGd8qESuuifuHsNjFPR-Va3P80bxrw+LqvC8deA8GziUJLpw@mail.gmail.com/ Cc: stable@vger.kernel.org Reviewed-by: Douglas Anderson Reviewed-by: Justin Stitt Tested-by: Justin Stitt Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-1-f236dbe9828d@linaro.org Signed-off-by: Daniel Thompson Signed-off-by: Greg Kroah-Hartman --- kernel/debug/kdb/kdb_io.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 6735ac36b..dcc7e13e9 100755 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -354,14 +354,19 @@ poll_again: 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; - kdb_printf("%s", cp); - cp += len; - lastchar += 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_tmp; + lastchar += len_tmp; + } } kdb_nextline = 1; /* reset output line number */ break;