Hi Jens,
After merging the block tree, today's linux-next build (powerpc
allnoconfig) failed like this:
fs/fcntl.o: In function `do_fcntl':
fcntl.c:(.text+0x6d4): undefined reference to `__get_user_bad'
fcntl.c:(.text+0x730): undefined reference to `__get_user_bad'
Probably caused by commit
c75b1d9421f8 ("fs: add fcntl() interface for setting/getting write life time hints")
On powerpc (at least) you cannot use get_user() to fetch anything larger
than "unsigned long" i.e. 32 bits on 32 bit powerpc.
This has been discussed before (and, I think, a fix attempted).
For now I have applied the following patch:
From: Stephen Rothwell <[email protected]>
Date: Wed, 28 Jun 2017 17:50:31 +1000
Subject: [PATCH] fs: don't read an enum directly from a u64 __user *
Signed-off-by: Stephen Rothwell <[email protected]>
---
fs/fcntl.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 24e233c75a33..19825eb7c40d 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -277,6 +277,7 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd,
{
struct inode *inode = file_inode(file);
u64 *argp = (u64 __user *)arg;
+ u64 h;
enum rw_hint hint;
switch (cmd) {
@@ -285,8 +286,9 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd,
return -EFAULT;
return 0;
case F_SET_FILE_RW_HINT:
- if (get_user(hint, argp))
+ if (copy_from_user(&h, argp, sizeof(h)))
return -EFAULT;
+ hint = (enum rw_hint)h;
if (!rw_hint_valid(hint))
return -EINVAL;
@@ -299,8 +301,9 @@ static long fcntl_rw_hint(struct file *file, unsigned int cmd,
return -EFAULT;
return 0;
case F_SET_RW_HINT:
- if (get_user(hint, argp))
+ if (copy_from_user(&h, argp, sizeof(h)))
return -EFAULT;
+ hint = (enum rw_hint)h;
if (!rw_hint_valid(hint))
return -EINVAL;
--
2.11.0
--
Cheers,
Stephen Rothwell
On 06/28/2017 02:04 AM, Stephen Rothwell wrote:
> Hi Jens,
>
> After merging the block tree, today's linux-next build (powerpc
> allnoconfig) failed like this:
>
> fs/fcntl.o: In function `do_fcntl':
> fcntl.c:(.text+0x6d4): undefined reference to `__get_user_bad'
> fcntl.c:(.text+0x730): undefined reference to `__get_user_bad'
>
> Probably caused by commit
>
> c75b1d9421f8 ("fs: add fcntl() interface for setting/getting write life time hints")
>
> On powerpc (at least) you cannot use get_user() to fetch anything larger
> than "unsigned long" i.e. 32 bits on 32 bit powerpc.
>
> This has been discussed before (and, I think, a fix attempted).
Gah, thanks for letting me know. I'll test your patch and queue it
up to fix this issue.
--
Jens Axboe
On 06/28/2017 06:43 AM, Jens Axboe wrote:
> On 06/28/2017 02:04 AM, Stephen Rothwell wrote:
>> Hi Jens,
>>
>> After merging the block tree, today's linux-next build (powerpc
>> allnoconfig) failed like this:
>>
>> fs/fcntl.o: In function `do_fcntl':
>> fcntl.c:(.text+0x6d4): undefined reference to `__get_user_bad'
>> fcntl.c:(.text+0x730): undefined reference to `__get_user_bad'
>>
>> Probably caused by commit
>>
>> c75b1d9421f8 ("fs: add fcntl() interface for setting/getting write life time hints")
>>
>> On powerpc (at least) you cannot use get_user() to fetch anything larger
>> than "unsigned long" i.e. 32 bits on 32 bit powerpc.
>>
>> This has been discussed before (and, I think, a fix attempted).
>
> Gah, thanks for letting me know. I'll test your patch and queue it
> up to fix this issue.
But put_user() is fine? Just checking here, since the change adds
both a u64 put and get user.
--
Jens Axboe
On 06/28/2017 08:01 AM, Jens Axboe wrote:
> On 06/28/2017 06:43 AM, Jens Axboe wrote:
>> On 06/28/2017 02:04 AM, Stephen Rothwell wrote:
>>> Hi Jens,
>>>
>>> After merging the block tree, today's linux-next build (powerpc
>>> allnoconfig) failed like this:
>>>
>>> fs/fcntl.o: In function `do_fcntl':
>>> fcntl.c:(.text+0x6d4): undefined reference to `__get_user_bad'
>>> fcntl.c:(.text+0x730): undefined reference to `__get_user_bad'
>>>
>>> Probably caused by commit
>>>
>>> c75b1d9421f8 ("fs: add fcntl() interface for setting/getting write life time hints")
>>>
>>> On powerpc (at least) you cannot use get_user() to fetch anything larger
>>> than "unsigned long" i.e. 32 bits on 32 bit powerpc.
>>>
>>> This has been discussed before (and, I think, a fix attempted).
>>
>> Gah, thanks for letting me know. I'll test your patch and queue it
>> up to fix this issue.
>
> But put_user() is fine? Just checking here, since the change adds
> both a u64 put and get user.
I just changed all 4, at least that provides some symmetry in how
we copy things in and out for that set of fcntls.
--
Jens Axboe
Hi Jens,
On Wed, 28 Jun 2017 09:11:32 -0600 Jens Axboe <[email protected]> wrote:
>
> On 06/28/2017 08:01 AM, Jens Axboe wrote:
> > But put_user() is fine? Just checking here, since the change adds
> > both a u64 put and get user.
Yes, put_user is fine (it does 2 4 byte moves. The asm is there to do
the 8 byte get_user, but the surrounding C code uses an unsigned long
for the destination in all cases (some other arches do the same). I
don't remember why it is like that.
> I just changed all 4, at least that provides some symmetry in how
> we copy things in and out for that set of fcntls.
OK, thanks.
--
Cheers,
Stephen Rothwell