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printk: fix illegal pbufs access for !CONFIG_PRINTK 

When CONFIG_PRINTK is not set, PRINTK_MESSAGE_MAX is 0. This
leads to a zero-sized array @outbuf in @printk_shared_pbufs. In
console_flush_all() a pointer to the first element of the array
is assigned with:

   char *outbuf = &printk_shared_pbufs.outbuf[0];

For !CONFIG_PRINTK this leads to a compiler warning:

   warning: array subscript 0 is outside array bounds of
   'char[0]' [-Warray-bounds]

This is not really dangerous because printk_get_next_message()
always returns false for !CONFIG_PRINTK, which leads to @outbuf
never being used. However, it makes no sense to even compile
these functions for !CONFIG_PRINTK.

Extend the existing '#ifdef CONFIG_PRINTK' block to contain
the formatting and emitting functions since these have no
purpose in !CONFIG_PRINTK. This also allows removing several
more !CONFIG_PRINTK dummies as well as moving
@suppress_panic_printk into a CONFIG_PRINTK block.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309201724.M9BMAQIh-lkp@intel.com/
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20230920155238.670439-1-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2023-09-20 17:58:38 +02:06 committed by Petr Mladek
parent 9757acd0a7
commit 98a0465531
1 changed files with 18 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
kernel/printk/printk.c
View File

@ -102,12 +102,6 @@ DEFINE_STATIC_SRCU(console_srcu);
*/
int __read_mostly suppress_printk;
/*
* During panic, heavy printk by other CPUs can delay the
* panic and risk deadlock on console resources.
*/
static int __read_mostly suppress_panic_printk;
#ifdef CONFIG_LOCKDEP
static struct lockdep_map console_lock_dep_map = {
.name = "console_lock"
@ -445,6 +439,12 @@ static int console_msg_format = MSG_FORMAT_DEFAULT;
static DEFINE_MUTEX(syslog_lock);
#ifdef CONFIG_PRINTK
/*
* During panic, heavy printk by other CPUs can delay the
* panic and risk deadlock on console resources.
*/
static int __read_mostly suppress_panic_printk;
DECLARE_WAIT_QUEUE_HEAD(log_wait);
/* All 3 protected by @syslog_lock. */
/* the next printk record to read by syslog(READ) or /proc/kmsg */
@ -2346,22 +2346,6 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
static u64 syslog_seq;
static size_t record_print_text(const struct printk_record *r,
bool syslog, bool time)
{
return 0;
}
static ssize_t info_print_ext_header(char *buf, size_t size,
struct printk_info *info)
{
return 0;
}
static ssize_t msg_print_ext_body(char *buf, size_t size,
char *text, size_t text_len,
struct dev_printk_info *dev_info) { return 0; }
static void console_lock_spinning_enable(void) { }
static int console_lock_spinning_disable_and_check(int cookie) { return 0; }
static bool suppress_message_printing(int level) { return false; }
static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
@ -2715,6 +2699,8 @@ static void __console_unlock(void)
up_console_sem();
}
#ifdef CONFIG_PRINTK
/*
* Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This
* is achieved by shifting the existing message over and inserting the dropped
@ -2729,7 +2715,6 @@ static void __console_unlock(void)
*
* If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
*/
#ifdef CONFIG_PRINTK
void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
{
struct printk_buffers *pbufs = pmsg->pbufs;
@ -2761,9 +2746,6 @@ void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
memcpy(outbuf, scratchbuf, len);
pmsg->outbuf_len += len;
}
#else
#define console_prepend_dropped(pmsg, dropped)
#endif /* CONFIG_PRINTK */
/*
* Read and format the specified record (or a later record if the specified
@ -2921,6 +2903,16 @@ skip:
return true;
}
#else
static bool console_emit_next_record(struct console *con, bool *handover, int cookie)
{
*handover = false;
return false;
}
#endif /* CONFIG_PRINTK */
/*
* Print out all remaining records to all consoles.
*