[syslinux] [PATCH 15/20] exit.c: Truncate exit status to uint8_t
Matt Fleming
matt at console-pimps.org
Sat Apr 16 07:17:43 PDT 2011
From: Matt Fleming <matt.fleming at linux.intel.com>
The valid range for an exit status is 0 - 255, so we need to truncate
the value passed to _exit().
I noticed this when a module was doing _exit(-1), and ended up calling
longjmp(.., 0xffffffff + 1)
which meant that setjmp() in spawn_load() returned 0. Obviously, we
wanted the setjmp() to return 256 (0xff + 1), because the code in
spawn_load() handles the return value like so,
ret_val = setjmp(module->u.x.process_exit);
if (ret_val)
ret_val--; /* Valid range is 0-255 */
else if (!module->main_func)
ret_val = -1;
else
exit((module->main_func)(argc, argv)); /* Actually run! */
There actually is code in spawn_load() to properly truncate 'ret_val',
but it is applied too late. The truncation needs to happen when we
pass the exit status to longjmp().
Suggested-by: H. Peter Anvin <hpa at zytor.com>
Signed-off-by: Matt Fleming <matt.fleming at linux.intel.com>
---
com32/lib/exit.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/com32/lib/exit.c b/com32/lib/exit.c
index cba6cee..ebec0a1 100644
--- a/com32/lib/exit.c
+++ b/com32/lib/exit.c
@@ -54,6 +54,6 @@ __noreturn _Exit(int rv)
__noreturn _exit(int rv)
{
- longjmp(__syslinux_current->u.x.process_exit, rv+1);
+ longjmp(__syslinux_current->u.x.process_exit, (uint8_t)rv+1);
}
--
1.7.4.2
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