From eaf06b241b091357e72b76863ba16e89610d31bd Mon Sep 17 00:00:00 2001 From: Dan Rosenberg Date: Thu, 11 Nov 2010 14:05:18 -0800 Subject: Restrict unprivileged access to kernel syslog The kernel syslog contains debugging information that is often useful during exploitation of other vulnerabilities, such as kernel heap addresses. Rather than futilely attempt to sanitize hundreds (or thousands) of printk statements and simultaneously cripple useful debugging functionality, it is far simpler to create an option that prevents unprivileged users from reading the syslog. This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the dmesg_restrict sysctl. When set to "0", the default, no restrictions are enforced. When set to "1", only users with CAP_SYS_ADMIN can read the kernel syslog via dmesg(8) or other mechanisms. [akpm@linux-foundation.org: explain the config option in kernel.txt] Signed-off-by: Dan Rosenberg Acked-by: Ingo Molnar Acked-by: Eugene Teo Acked-by: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index b526947bdf48..fc3da9e4da19 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -293,6 +293,7 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, unsigned int interval_msec); extern int printk_delay_msec; +extern int dmesg_restrict; /* * Print a one-time message (analogous to WARN_ONCE() et al): -- cgit v1.2.2 From 968ab1838a5d48f02f5b471aa1d0e59e2cc2ccbc Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 15 Nov 2010 13:37:37 -0800 Subject: include/linux/kernel.h: Move logging bits to include/linux/printk.h Move the logging bits from kernel.h into printk.h so that there is a bit more logical separation of the generic from the printk logging specific parts. Signed-off-by: Joe Perches Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 245 +------------------------------------------------ 1 file changed, 1 insertion(+), 244 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index fc3da9e4da19..b6de9a6f7018 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -17,13 +17,11 @@ #include #include #include +#include #include #include #include -extern const char linux_banner[]; -extern const char linux_proc_banner[]; - #define USHRT_MAX ((u16)(~0U)) #define SHRT_MAX ((s16)(USHRT_MAX>>1)) #define SHRT_MIN ((s16)(-SHRT_MAX - 1)) @@ -110,31 +108,6 @@ extern const char linux_proc_banner[]; */ #define lower_32_bits(n) ((u32)(n)) -#define KERN_EMERG "<0>" /* system is unusable */ -#define KERN_ALERT "<1>" /* action must be taken immediately */ -#define KERN_CRIT "<2>" /* critical conditions */ -#define KERN_ERR "<3>" /* error conditions */ -#define KERN_WARNING "<4>" /* warning conditions */ -#define KERN_NOTICE "<5>" /* normal but significant condition */ -#define KERN_INFO "<6>" /* informational */ -#define KERN_DEBUG "<7>" /* debug-level messages */ - -/* Use the default kernel loglevel */ -#define KERN_DEFAULT "" -/* - * Annotation for a "continued" line of log printout (only done after a - * line that had no enclosing \n). Only to be used by core/arch code - * during early bootup (a continued line is not SMP-safe otherwise). - */ -#define KERN_CONT "" - -extern int console_printk[]; - -#define console_loglevel (console_printk[0]) -#define default_message_loglevel (console_printk[1]) -#define minimum_console_loglevel (console_printk[2]) -#define default_console_loglevel (console_printk[3]) - struct completion; struct pt_regs; struct user; @@ -187,11 +160,6 @@ static inline void might_fault(void) } #endif -struct va_format { - const char *fmt; - va_list *va; -}; - extern struct atomic_notifier_head panic_notifier_list; extern long (*panic_blink)(int state); NORET_TYPE void panic(const char * fmt, ...) @@ -245,115 +213,8 @@ extern int func_ptr_is_kernel_text(void *ptr); struct pid; extern struct pid *session_of_pgrp(struct pid *pgrp); -/* - * FW_BUG - * Add this to a message where you are sure the firmware is buggy or behaves - * really stupid or out of spec. Be aware that the responsible BIOS developer - * should be able to fix this issue or at least get a concrete idea of the - * problem by reading your message without the need of looking at the kernel - * code. - * - * Use it for definite and high priority BIOS bugs. - * - * FW_WARN - * Use it for not that clear (e.g. could the kernel messed up things already?) - * and medium priority BIOS bugs. - * - * FW_INFO - * Use this one if you want to tell the user or vendor about something - * suspicious, but generally harmless related to the firmware. - * - * Use it for information or very low priority BIOS bugs. - */ -#define FW_BUG "[Firmware Bug]: " -#define FW_WARN "[Firmware Warn]: " -#define FW_INFO "[Firmware Info]: " - -/* - * HW_ERR - * Add this to a message for hardware errors, so that user can report - * it to hardware vendor instead of LKML or software vendor. - */ -#define HW_ERR "[Hardware Error]: " - -#ifdef CONFIG_PRINTK -asmlinkage int vprintk(const char *fmt, va_list args) - __attribute__ ((format (printf, 1, 0))); -asmlinkage int printk(const char * fmt, ...) - __attribute__ ((format (printf, 1, 2))) __cold; - -/* - * Please don't use printk_ratelimit(), because it shares ratelimiting state - * with all other unrelated printk_ratelimit() callsites. Instead use - * printk_ratelimited() or plain old __ratelimit(). - */ -extern int __printk_ratelimit(const char *func); -#define printk_ratelimit() __printk_ratelimit(__func__) -extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, - unsigned int interval_msec); - -extern int printk_delay_msec; -extern int dmesg_restrict; - -/* - * Print a one-time message (analogous to WARN_ONCE() et al): - */ -#define printk_once(x...) ({ \ - static bool __print_once; \ - \ - if (!__print_once) { \ - __print_once = true; \ - printk(x); \ - } \ -}) - -void log_buf_kexec_setup(void); -#else -static inline int vprintk(const char *s, va_list args) - __attribute__ ((format (printf, 1, 0))); -static inline int vprintk(const char *s, va_list args) { return 0; } -static inline int printk(const char *s, ...) - __attribute__ ((format (printf, 1, 2))); -static inline int __cold printk(const char *s, ...) { return 0; } -static inline int printk_ratelimit(void) { return 0; } -static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \ - unsigned int interval_msec) \ - { return false; } - -/* No effect, but we still get type checking even in the !PRINTK case: */ -#define printk_once(x...) printk(x) - -static inline void log_buf_kexec_setup(void) -{ -} -#endif - -/* - * Dummy printk for disabled debugging statements to use whilst maintaining - * gcc's format and side-effect checking. - */ -static inline __attribute__ ((format (printf, 1, 2))) -int no_printk(const char *s, ...) { return 0; } - -extern int printk_needs_cpu(int cpu); -extern void printk_tick(void); - -extern void asmlinkage __attribute__((format(printf, 1, 2))) - early_printk(const char *fmt, ...); - unsigned long int_sqrt(unsigned long); -static inline void console_silent(void) -{ - console_loglevel = 0; -} - -static inline void console_verbose(void) -{ - if (console_loglevel) - console_loglevel = 15; -} - extern void bust_spinlocks(int yes); extern void wake_up_klogd(void); extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */ @@ -390,22 +251,6 @@ extern enum system_states { #define TAINT_CRAP 10 #define TAINT_FIRMWARE_WORKAROUND 11 -extern void dump_stack(void) __cold; - -enum { - DUMP_PREFIX_NONE, - DUMP_PREFIX_ADDRESS, - DUMP_PREFIX_OFFSET -}; -extern void hex_dump_to_buffer(const void *buf, size_t len, - int rowsize, int groupsize, - char *linebuf, size_t linebuflen, bool ascii); -extern void print_hex_dump(const char *level, const char *prefix_str, - int prefix_type, int rowsize, int groupsize, - const void *buf, size_t len, bool ascii); -extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type, - const void *buf, size_t len); - extern const char hex_asc[]; #define hex_asc_lo(x) hex_asc[((x) & 0x0f)] #define hex_asc_hi(x) hex_asc[((x) & 0xf0) >> 4] @@ -419,94 +264,6 @@ static inline char *pack_hex_byte(char *buf, u8 byte) extern int hex_to_bin(char ch); -#ifndef pr_fmt -#define pr_fmt(fmt) fmt -#endif - -#define pr_emerg(fmt, ...) \ - printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) -#define pr_alert(fmt, ...) \ - printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_crit(fmt, ...) \ - printk(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_err(fmt, ...) \ - printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warning(fmt, ...) \ - printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warn pr_warning -#define pr_notice(fmt, ...) \ - printk(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__) -#define pr_info(fmt, ...) \ - printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) -#define pr_cont(fmt, ...) \ - printk(KERN_CONT fmt, ##__VA_ARGS__) - -/* pr_devel() should produce zero code unless DEBUG is defined */ -#ifdef DEBUG -#define pr_devel(fmt, ...) \ - printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#else -#define pr_devel(fmt, ...) \ - ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) -#endif - -/* If you are writing a driver, please use dev_dbg instead */ -#if defined(DEBUG) -#define pr_debug(fmt, ...) \ - printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#elif defined(CONFIG_DYNAMIC_DEBUG) -/* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */ -#define pr_debug(fmt, ...) \ - dynamic_pr_debug(fmt, ##__VA_ARGS__) -#else -#define pr_debug(fmt, ...) \ - ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) -#endif - -/* - * ratelimited messages with local ratelimit_state, - * no local ratelimit_state used in the !PRINTK case - */ -#ifdef CONFIG_PRINTK -#define printk_ratelimited(fmt, ...) ({ \ - static DEFINE_RATELIMIT_STATE(_rs, \ - DEFAULT_RATELIMIT_INTERVAL, \ - DEFAULT_RATELIMIT_BURST); \ - \ - if (__ratelimit(&_rs)) \ - printk(fmt, ##__VA_ARGS__); \ -}) -#else -/* No effect, but we still get type checking even in the !PRINTK case: */ -#define printk_ratelimited printk -#endif - -#define pr_emerg_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) -#define pr_alert_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_crit_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_err_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warning_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warn_ratelimited pr_warning_ratelimited -#define pr_notice_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__) -#define pr_info_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) -/* no pr_cont_ratelimited, don't do that... */ -/* If you are writing a driver, please use dev_dbg instead */ -#if defined(DEBUG) -#define pr_debug_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#else -#define pr_debug_ratelimited(fmt, ...) \ - ({ if (0) printk_ratelimited(KERN_DEBUG pr_fmt(fmt), \ - ##__VA_ARGS__); 0; }) -#endif - /* * General tracing related utility functions - trace_printk(), * tracing_on/tracing_off and tracing_start()/tracing_stop -- cgit v1.2.2