From 9f36e2c448007b54851e7e4fa48da97d1477a175 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 22 Mar 2011 16:34:22 -0700 Subject: [PATCH] printk: use %pK for /proc/kallsyms and /proc/modules In an effort to reduce kernel address leaks that might be used to help target kernel privilege escalation exploits, this patch uses %pK when displaying addresses in /proc/kallsyms, /proc/modules, and /sys/module/*/sections/*. Note that this changes %x to %p, so some legitimately 0 values in /proc/kallsyms would have changed from 00000000 to "(null)". To avoid this, "(null)" is not used when using the "K" format. Anything that was already successfully parsing "(null)" in addition to full hex digits should have no problem with this change. (Thanks to Joe Perches for the suggestion.) Due to the %x to %p, "void *" casts are needed since these addresses are already "unsigned long" everywhere internally, due to their starting life as ELF section offsets. Signed-off-by: Kees Cook Cc: Eugene Teo Cc: Dan Rosenberg Cc: Rusty Russell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kallsyms.c | 10 ++++------ kernel/module.c | 4 ++-- lib/vsprintf.c | 2 +- 3 files changed, 7 insertions(+), 9 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 6f6d091b5757..75dcca37d61a 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -477,13 +477,11 @@ static int s_show(struct seq_file *m, void *p) */ type = iter->exported ? toupper(iter->type) : tolower(iter->type); - seq_printf(m, "%0*lx %c %s\t[%s]\n", - (int)(2 * sizeof(void *)), - iter->value, type, iter->name, iter->module_name); + seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value, + type, iter->name, iter->module_name); } else - seq_printf(m, "%0*lx %c %s\n", - (int)(2 * sizeof(void *)), - iter->value, iter->type, iter->name); + seq_printf(m, "%pK %c %s\n", (void *)iter->value, + iter->type, iter->name); return 0; } diff --git a/kernel/module.c b/kernel/module.c index efa290ea94bf..1f9f7bc56ca1 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1168,7 +1168,7 @@ static ssize_t module_sect_show(struct module_attribute *mattr, { struct module_sect_attr *sattr = container_of(mattr, struct module_sect_attr, mattr); - return sprintf(buf, "0x%lx\n", sattr->address); + return sprintf(buf, "0x%pK\n", (void *)sattr->address); } static void free_sect_attrs(struct module_sect_attrs *sect_attrs) @@ -3224,7 +3224,7 @@ static int m_show(struct seq_file *m, void *p) mod->state == MODULE_STATE_COMING ? "Loading": "Live"); /* Used by oprofile and other similar tools. */ - seq_printf(m, " 0x%p", mod->module_core); + seq_printf(m, " 0x%pK", mod->module_core); /* Taints info */ if (mod->taints) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 070d134eef71..ac444ff01658 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -991,7 +991,7 @@ static noinline_for_stack char *pointer(const char *fmt, char *buf, char *end, void *ptr, struct printf_spec spec) { - if (!ptr) { + if (!ptr && *fmt != 'K') { /* * Print (null) with the same width as a pointer so it makes * tabular output look nice.