[uml-devel] [PATCH 3/5] uml: clear SKAS0/3 flags when running in TT mode

[Paolo 'B. G. <bla...@ya...>]

From: Paolo 'Blaisorblade' Giarrusso <bla...@ya...>

SEGV_MAYBE_FIXABLE tests ptrace_faultinfo, and depends on it being 1 only in
SKAS3 mode, while currently when running with mode=tt it will be 1 anyway. Fix
this, and do the same for proc_mm.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <bla...@ya...>
---

 arch/um/include/os.h     |    4 ++++
 arch/um/kernel/um_arch.c |    2 ++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/um/include/os.h b/arch/um/include/os.h
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -157,6 +157,10 @@ extern int os_lock_file(int fd, int excl
 extern void os_early_checks(void);
 extern int can_do_skas(void);
 
+/* Make sure they are clear when running in TT mode. Required by
+ * SEGV_MAYBE_FIXABLE */
+#define clear_can_do_skas() do { ptrace_faultinfo = proc_mm = 0; } while (0)
+
 /* mem.c */
 extern int create_mem_file(unsigned long len);
 
diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
--- a/arch/um/kernel/um_arch.c
+++ b/arch/um/kernel/um_arch.c
@@ -334,6 +334,8 @@ int linux_main(int argc, char **argv)
 		add_arg(DEFAULT_COMMAND_LINE);
 
 	os_early_checks();
+	if (force_tt)
+		clear_can_do_skas();
 	mode_tt = force_tt ? 1 : !can_do_skas();
 #ifndef CONFIG_MODE_TT
 	if (mode_tt) {