* [PATCH] module: report -EFAULT on bytes remaining
@ 2012-09-12 15:06 Kees Cook
2012-09-12 15:40 ` Dan Carpenter
0 siblings, 1 reply; 3+ messages in thread
From: Kees Cook @ 2012-09-12 15:06 UTC (permalink / raw)
To: linux-kernel
Cc: Rusty Russell, Fengguang Wu, kernel-janitors, Mimi Zohar,
Dan Carpenter
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@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
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)
--
1.7.0.4
--
Kees Cook
Chrome OS Security
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] module: report -EFAULT on bytes remaining
2012-09-12 15:06 [PATCH] module: report -EFAULT on bytes remaining Kees Cook
@ 2012-09-12 15:40 ` Dan Carpenter
2012-09-13 6:43 ` Rusty Russell
0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2012-09-12 15:40 UTC (permalink / raw)
To: Kees Cook
Cc: linux-kernel, Rusty Russell, Fengguang Wu, kernel-janitors,
Mimi Zohar
On Wed, Sep 12, 2012 at 08:06:16AM -0700, Kees Cook wrote:
> 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@intel.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> 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)
^^^^^^^^^^^
This condition is always true because copy_to/from_user() returns
the number of bytes remaining to be copied. (It never returns a
negative error code).
> + err = -EFAULT;
> goto free_hdr;
> + }
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] module: report -EFAULT on bytes remaining
2012-09-12 15:40 ` Dan Carpenter
@ 2012-09-13 6:43 ` Rusty Russell
0 siblings, 0 replies; 3+ messages in thread
From: Rusty Russell @ 2012-09-13 6:43 UTC (permalink / raw)
To: Dan Carpenter, Kees Cook
Cc: linux-kernel, Fengguang Wu, kernel-janitors, Mimi Zohar
Dan Carpenter <dan.carpenter@oracle.com> writes:
> On Wed, Sep 12, 2012 at 08:06:16AM -0700, Kees Cook wrote:
>> 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@intel.com>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>> 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)
> ^^^^^^^^^^^
> This condition is always true because copy_to/from_user() returns
> the number of bytes remaining to be copied. (It never returns a
> negative error code).
Yes, I made the obvious fix (eliminating the >0 check).
This "copy_from_user is stupid" was a debate a lost long ago, but it
still annoys me.
Applied,
Rusty.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-09-12 15:40 ` Dan Carpenter
2012-09-13 6:43 ` Rusty Russell
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