Ensure the entries of a payload exception table only apply to text regions in
the payload itself. Since the payload exception table needs to be loaded and
active even before a patch is applied (because hooks might already rely on it),
make sure the exception table (if any) only contains fixups for the payload
text section.
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
Reviewed-by: Jan Beulich <jbeul...@suse.com>
---
Changes since v3:
- Rename to extable_in_bounds().
- Use _p() instead of casting to void *.
Changes since v2:
- New in this version.
---
xen/arch/x86/extable.c | 18 ++++++++++++++++++
xen/arch/x86/include/asm/uaccess.h | 3 +++
xen/common/livepatch.c | 9 +++++++++
3 files changed, 30 insertions(+)
diff --git a/xen/arch/x86/extable.c b/xen/arch/x86/extable.c
index 8415cd1fa249..2be090b92df8 100644
--- a/xen/arch/x86/extable.c
+++ b/xen/arch/x86/extable.c
@@ -228,3 +228,21 @@ unsigned long asmlinkage search_pre_exception_table(struct
cpu_user_regs *regs)
}
return fixup;
}
+
+#ifdef CONFIG_LIVEPATCH
+bool extable_in_bounds(const struct exception_table_entry *ex_start,
+ const struct exception_table_entry *ex_end,
+ const void *start, const void *end)
+{
+ for ( ; ex_start < ex_end; ex_start++ )
+ {
+ const void *addr = _p(ex_addr(ex_start));
+ const void *cont = _p(ex_cont(ex_start));
+
+ if ( addr < start || addr >= end || cont < start || cont >= end )
+ return false;
+ }
+
+ return true;
+}
+#endif
diff --git a/xen/arch/x86/include/asm/uaccess.h
b/xen/arch/x86/include/asm/uaccess.h
index 48b684c19d44..4995edfdd8db 100644
--- a/xen/arch/x86/include/asm/uaccess.h
+++ b/xen/arch/x86/include/asm/uaccess.h
@@ -426,5 +426,8 @@ extern unsigned long search_exception_table(const struct
cpu_user_regs *regs,
extern void sort_exception_tables(void);
extern void sort_exception_table(struct exception_table_entry *start,
const struct exception_table_entry *stop);
+extern bool extable_in_bounds(const struct exception_table_entry *ex_start,
+ const struct exception_table_entry *ex_end,
+ const void *start, const void *end);
#endif /* __X86_UACCESS_H__ */
diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index 1afde0281402..4702c06902a9 100644
--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -912,6 +912,15 @@ static int prepare_payload(struct payload *payload,
s = sec->load_addr;
e = sec->load_addr + sec->sec->sh_size;
+ if ( !extable_in_bounds(s, e, payload->text_addr,
+ payload->text_addr + payload->text_size) )
+ {
+ printk(XENLOG_ERR LIVEPATCH
+ "%s: Invalid exception table with out of bounds entries\n",
+ elf->name);
+ return -EINVAL;
+ }
+
sort_exception_table(s ,e);
region->ex = s;
--
2.44.0
