diff options
| author | Daniel Thompson <daniel.thompson@linaro.org> | 2020-02-13 15:16:40 +0000 |
|---|---|---|
| committer | Daniel Thompson <daniel.thompson@linaro.org> | 2020-04-01 16:59:11 +0100 |
| commit | ad99b5105c0823ff02126497f4366e6a8009453e (patch) | |
| tree | 44e3f94cbac26b7e9208a2b4b1cabb30c77acabc | |
| parent | d228bee8201a7ea77c414f1298b2f572f42c6113 (diff) | |
kdb: Censor attempts to set PROMPT without ENABLE_MEM_READ
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>
| -rw-r--r-- | kernel/debug/kdb/kdb_main.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index a4641be4123c..515379cbf209 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) 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 */ if (strcmp(argv[1], "KDBDEBUG") == 0) { @@ -1298,12 +1305,9 @@ 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); |