[PATCH] module: report -EFAULT on bytes remaining

From: Kees Cook
Date: Wed Sep 12 2012 - 11:06:37 EST

Caught by smatch:
kernel/module.c:2450 copy_module_from_user() warn: maybe return -EFAULT instead of the bytes remaining?

Clean up the copy_from_user() call to not report a positive value.
With this patch, init_module() will report errors from copy_from_user
(before it would always only report -EFAULT when err != 0).

Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
This change is on top of the finit_module patch series.
kernel/module.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 0ad03c4..05b8dde 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2441,8 +2441,11 @@ int copy_module_from_user(const void __user *umod, unsigned long len,
return -ENOMEM;

err = copy_from_user(info->hdr, umod, info->len);
- if (err)
+ if (err) {
+ if (err > 0)
+ err = -EFAULT;
goto free_hdr;
+ }

err = check_info(info);
if (err)

Kees Cook
Chrome OS Security
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/