Messages in this thread Patch in this message | | | Date | Tue, 25 Jan 2011 10:10:58 -0800 | From | Kees Cook <> | Subject | [PATCH] use %pK for /proc/kallsyms and /proc/modules |
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Instead of messing with permissions on these files, use %pK for kernel addresses to reduce potential information leaks that might be used to help target kernel privilege escalation exploits.
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 parsing such addresses should have no problem with this change. (Thanks to Joe Perches for the suggestion.)
Note that when compiling with -Wformat, these harmless warnings will be emitted, and can be ignored: warning: '0' flag used with ‘%p’ gnu_printf format
Signed-off-by: Kees Cook <kees.cook@canonical.com> --- kernel/kallsyms.c | 4 ++-- kernel/module.c | 4 ++-- lib/vsprintf.c | 2 +- 3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 6f6d091..074b762 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -477,11 +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", + seq_printf(m, "%0*pK %c %s\t[%s]\n", (int)(2 * sizeof(void *)), iter->value, type, iter->name, iter->module_name); } else - seq_printf(m, "%0*lx %c %s\n", + seq_printf(m, "%0*pK %c %s\n", (int)(2 * sizeof(void *)), iter->value, iter->type, iter->name); return 0; diff --git a/kernel/module.c b/kernel/module.c index 34e00b7..748465c 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", 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 d3023df..288d770 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. -- 1.7.2.3 -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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