x86: tls prevent_tail_call
Fix a kernel bug (vmware boot problem) reported by Tomasz Grobelny,
which occurs with certain .config variants and gccs.
The x86 TLS cleanup in commit efd1ca52d04d2f6df337a3332cee56cd60e6d4c4
made the sys_set_thread_area and sys_get_thread_area functions ripe for
tail call optimization. If the compiler chooses to use it for them, it
can clobber the user trap frame because these are asmlinkage functions.
Reported-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/tls.c b/arch/x86/kernel/tls.c
index 6dfd4e7..022bcaa 100644
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -91,7 +91,9 @@
asmlinkage int sys_set_thread_area(struct user_desc __user *u_info)
{
- return do_set_thread_area(current, -1, u_info, 1);
+ int ret = do_set_thread_area(current, -1, u_info, 1);
+ prevent_tail_call(ret);
+ return ret;
}
@@ -139,7 +141,9 @@
asmlinkage int sys_get_thread_area(struct user_desc __user *u_info)
{
- return do_get_thread_area(current, -1, u_info);
+ int ret = do_get_thread_area(current, -1, u_info);
+ prevent_tail_call(ret);
+ return ret;
}
int regset_tls_active(struct task_struct *target,