From ad6561dffa17f17bb68d7207d422c26c381c4313 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 12 Jun 2009 21:47:03 -0600 Subject: module: trim exception table on init free. It's theoretically possible that there are exception table entries which point into the (freed) init text of modules. These could cause future problems if other modules get loaded into that memory and cause an exception as we'd see the wrong fixup. The only case I know of is kvm-intel.ko (when CONFIG_CC_OPTIMIZE_FOR_SIZE=n). Amerigo fixed this long-standing FIXME in the x86 version, but this patch is more general. This implements trim_init_extable(); most archs are simple since they use the standard lib/extable.c sort code. Alpha and IA64 use relative addresses in their fixups, so thier trimming is a slight variation. Sparc32 is unique; it doesn't seem to define ARCH_HAS_SORT_EXTABLE, yet it defines its own sort_extable() which overrides the one in lib. It doesn't sort, so we have to mark deleted entries instead of actually trimming them. Inspired-by: Amerigo Wang Signed-off-by: Rusty Russell Cc: linux-alpha@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: linux-ia64@vger.kernel.org --- lib/extable.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) (limited to 'lib/extable.c') diff --git a/lib/extable.c b/lib/extable.c index 179c08745595..4cac81ec225e 100644 --- a/lib/extable.c +++ b/lib/extable.c @@ -39,7 +39,26 @@ void sort_extable(struct exception_table_entry *start, sort(start, finish - start, sizeof(struct exception_table_entry), cmp_ex, NULL); } -#endif + +#ifdef CONFIG_MODULES +/* + * If the exception table is sorted, any referring to the module init + * will be at the beginning or the end. + */ +void trim_init_extable(struct module *m) +{ + /*trim the beginning*/ + while (m->num_exentries && within_module_init(m->extable[0].insn, m)) { + m->extable++; + m->num_exentries--; + } + /*trim the end*/ + while (m->num_exentries && + within_module_init(m->extable[m->num_exentries-1].insn, m)) + m->num_exentries--; +} +#endif /* CONFIG_MODULES */ +#endif /* !ARCH_HAS_SORT_EXTABLE */ #ifndef ARCH_HAS_SEARCH_EXTABLE /* -- cgit v1.2.2