linux-next: build failure after merge of the block tree

Stephen Rothwell
2017-06-28T08:05:12Z

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 <sfr@canb.auug.org.au>
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 <sfr@canb.auug.org.au>
---
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