4.19-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Thompson daniel.thompson@linaro.org
[ Upstream commit ad99b5105c0823ff02126497f4366e6a8009453e ]
Currently the PROMPT variable could be abused to provoke the printf() machinery to read outside the current stack frame. Normally this doesn't matter becaues md is already a much better tool for reading from memory.
However the md command can be disabled by not setting KDB_ENABLE_MEM_READ. Let's also prevent PROMPT from being modified in these circumstances.
Whilst adding a comment to help future code reviewers we also remove the #ifdef where PROMPT in consumed. There is no problem passing an unused (0) to snprintf when !CONFIG_SMP. argument
Reported-by: Wang Xiayang xywang.sjtu@sjtu.edu.cn Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Reviewed-by: Douglas Anderson dianders@chromium.org Stable-dep-of: 4f41d30cd6dc ("kdb: Fix a potential buffer overflow in kdb_local()") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/debug/kdb/kdb_main.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index dc6bf35e7884..8f31d472384f 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -399,6 +399,13 @@ int kdb_set(int argc, const char **argv) if (argc != 2) return KDB_ARGCOUNT;
+ /* + * Censor sensitive variables + */ + if (strcmp(argv[1], "PROMPT") == 0 && + !kdb_check_flags(KDB_ENABLE_MEM_READ, kdb_cmd_enabled, false)) + return KDB_NOPERM; + /* * Check for internal variables */ @@ -1299,12 +1306,9 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, *(cmd_hist[cmd_head]) = '\0';
do_full_getstr: -#if defined(CONFIG_SMP) + /* PROMPT can only be set if we have MEM_READ permission. */ snprintf(kdb_prompt_str, CMD_BUFLEN, kdbgetenv("PROMPT"), raw_smp_processor_id()); -#else - snprintf(kdb_prompt_str, CMD_BUFLEN, kdbgetenv("PROMPT")); -#endif if (defcmd_in_progress) strncat(kdb_prompt_str, "[defcmd]", CMD_BUFLEN);