diff options
Diffstat (limited to 'kernel/debug/kdb/kdb_main.c')
| -rw-r--r-- | kernel/debug/kdb/kdb_main.c | 76 |
1 files changed, 67 insertions, 9 deletions
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 4567fe998c30..51cfb8618205 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -45,6 +45,7 @@ #include <linux/proc_fs.h> #include <linux/uaccess.h> #include <linux/slab.h> +#include <linux/security.h> #include "kdb_private.h" #undef MODULE_PARAM_PREFIX @@ -198,10 +199,62 @@ struct task_struct *kdb_curr_task(int cpu) } /* - * Check whether the flags of the current command and the permissions - * of the kdb console has allow a command to be run. + * Update the permissions flags (kdb_cmd_enabled) to match the + * current lockdown state. + * + * Within this function the calls to security_locked_down() are "lazy". We + * avoid calling them if the current value of kdb_cmd_enabled already excludes + * flags that might be subject to lockdown. Additionally we deliberately check + * the lockdown flags independently (even though read lockdown implies write + * lockdown) since that results in both simpler code and clearer messages to + * the user on first-time debugger entry. + * + * The permission masks during a read+write lockdown permits the following + * flags: INSPECT, SIGNAL, REBOOT (and ALWAYS_SAFE). + * + * The INSPECT commands are not blocked during lockdown because they are + * not arbitrary memory reads. INSPECT covers the backtrace family (sometimes + * forcing them to have no arguments) and lsmod. These commands do expose + * some kernel state but do not allow the developer seated at the console to + * choose what state is reported. SIGNAL and REBOOT should not be controversial, + * given these are allowed for root during lockdown already. */ -static inline bool kdb_check_flags(kdb_cmdflags_t flags, int permissions, +static void kdb_check_for_lockdown(void) +{ + const int write_flags = KDB_ENABLE_MEM_WRITE | + KDB_ENABLE_REG_WRITE | + KDB_ENABLE_FLOW_CTRL; + const int read_flags = KDB_ENABLE_MEM_READ | + KDB_ENABLE_REG_READ; + + bool need_to_lockdown_write = false; + bool need_to_lockdown_read = false; + + if (kdb_cmd_enabled & (KDB_ENABLE_ALL | write_flags)) + need_to_lockdown_write = + security_locked_down(LOCKDOWN_DBG_WRITE_KERNEL); + + if (kdb_cmd_enabled & (KDB_ENABLE_ALL | read_flags)) + need_to_lockdown_read = + security_locked_down(LOCKDOWN_DBG_READ_KERNEL); + + /* De-compose KDB_ENABLE_ALL if required */ + if (need_to_lockdown_write || need_to_lockdown_read) + if (kdb_cmd_enabled & KDB_ENABLE_ALL) + kdb_cmd_enabled = KDB_ENABLE_MASK & ~KDB_ENABLE_ALL; + + if (need_to_lockdown_write) + kdb_cmd_enabled &= ~write_flags; + + if (need_to_lockdown_read) + kdb_cmd_enabled &= ~read_flags; +} + +/* + * Check whether the flags of the current command, the permissions of the kdb + * console and the lockdown state allow a command to be run. + */ +static bool kdb_check_flags(kdb_cmdflags_t flags, int permissions, bool no_args) { /* permissions comes from userspace so needs massaging slightly */ @@ -400,6 +453,13 @@ 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) { @@ -1188,6 +1248,9 @@ static int kdb_local(kdb_reason_t reason, int error, struct pt_regs *regs, kdb_curr_task(raw_smp_processor_id()); KDB_DEBUG_STATE("kdb_local 1", reason); + + kdb_check_for_lockdown(); + kdb_go_count = 0; if (reason == KDB_REASON_DEBUG) { /* special case below */ @@ -1299,14 +1362,9 @@ 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); /* * Fetch command from keyboard |