From: Daniel Thompson daniel.thompson@linaro.org

stable inclusion from stable-v5.10.219 commit cfdc2fa4db57503bc6d3817240547c8ddc55fa96 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 6735ac36b718..dcc7e13e98b3 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -354,14 +354,19 @@ 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;