From: Daniel Thompson daniel.thompson@linaro.org

stable inclusion from stable-v4.19.316 commit fb824a99e148ff272a53d71d84122728b5f00992 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAB05N CVE: CVE-2024-39480

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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 justinstitt@google.com Closes: https://lore.kernel.org/all/CAFhGd8qESuuifuHsNjFPR-Va3P80bxrw+LqvC8deA8GziUJ... Cc: stable@vger.kernel.org Reviewed-by: Douglas Anderson dianders@chromium.org Reviewed-by: Justin Stitt justinstitt@google.com Tested-by: Justin Stitt justinstitt@google.com Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-1-f236dbe9828d@lina... Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Fixes: 5d5314d6795f3c1c0f415348ff8c51f7de042b77 ("kdb: core for kgdb back end (1 of 2)") Signed-off-by: Tengda Wu wutengda2@huawei.com --- 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 6a4b41484afe..2ce307c86977 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -364,14 +364,19 @@ 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; - 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;