[PATCH v2] module: report -EFAULT on bytes remaining

From: Kees Cook
Date: Wed Sep 12 2012 - 12:21:28 EST

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

Fix the check of copy_from_user() to report -EFAULT as was done before.

Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Should be applied on top of the finit_module syscall patches.

- copy_from_user never returns negative, thanks to Dan Carpenter.
kernel/module.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 0ad03c4..461e7d4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2440,9 +2440,10 @@ int copy_module_from_user(const void __user *umod, unsigned long len,
if (!info->hdr)
return -ENOMEM;

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

err = check_info(info);
if (err)

Kees Cook
Chrome OS Security
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