%p has many modifiers where the pointer is dereferenced. An invalid pointer might cause kernel to crash silently.
Note that printk() formats the string under logbuf_lock. Any recursive printks are redirected to the printk_safe implementation and the messages are stored into per-CPU buffers. These buffers might be eventually flushed in printk_safe_flush_on_panic() but it is not guaranteed. In general, we should do our best to get useful message from printk(). All pointers to the first memory page must be invalid. Let's prevent the dereference and print "(null)" in this case. This is already done in many other situations, including "%s" format handling and many page fault handlers. Signed-off-by: Petr Mladek <pmla...@suse.com> --- lib/vsprintf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index d7a708f82559..5c2d1f44218a 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1849,7 +1849,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, { const int default_width = 2 * sizeof(void *); - if (!ptr && *fmt != 'K' && *fmt != 'x') { + if ((unsigned long)ptr < PAGE_SIZE && *fmt != 'K' && *fmt != 'x') { /* * Print (null) with the same width as a pointer so it makes * tabular output look nice. -- 2.13.6