[PATCH] staging/lustre/lov: remove set_fs() call from lov_getstripe()

[PATCH] staging/lustre/lov: remove set_fs() call from lov_getstripe()

[Oleg Drokin]

lov_getstripe() calls set_fs(KERNEL_DS) so that it can handle a struct
lov_user_md pointer from user- or kernel-space.  This changes the
behavior of copy_from_user() on SPARC and may result in a misaligned
access exception which in turn oopses the kernel.  In fact the
relevant argument to lov_getstripe() is never called with a
kernel-space pointer and so changing the address limits is unnecessary
and so we remove the calls to save, set, and restore the address
limits.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Reviewed-on: http://review.whamcloud.com/6150
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3221
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
---
 drivers/staging/lustre/lustre/lov/lov_pack.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/staging/lustre/lustre/lov/lov_pack.c b/drivers/staging/lustre/lustre/lov/lov_pack.c
index 2e1bd47..e6727ce 100644
--- a/drivers/staging/lustre/lustre/lov/lov_pack.c
+++ b/drivers/staging/lustre/lustre/lov/lov_pack.c
@@ -293,18 +293,10 @@ int lov_getstripe(struct lov_object *obj, struct lov_stripe_md *lsm,
 	size_t lmmk_size;
 	size_t lum_size;
 	int rc;
-	mm_segment_t seg;
 
 	if (!lsm)
 		return -ENODATA;
 
-	/*
-	 * "Switch to kernel segment" to allow copying from kernel space by
-	 * copy_{to,from}_user().
-	 */
-	seg = get_fs();
-	set_fs(KERNEL_DS);
-
 	if (lsm->lsm_magic != LOV_MAGIC_V1 && lsm->lsm_magic != LOV_MAGIC_V3) {
 		CERROR("bad LSM MAGIC: 0x%08X != 0x%08X nor 0x%08X\n",
 		       lsm->lsm_magic, LOV_MAGIC_V1, LOV_MAGIC_V3);
@@ -406,6 +398,5 @@ int lov_getstripe(struct lov_object *obj, struct lov_stripe_md *lsm,
 out_free:
 	kvfree(lmmk);
 out:
-	set_fs(seg);
 	return rc;
 }
-- 
2.9.3

Re: [PATCH] staging/lustre/lov: remove set_fs() call from lov_getstripe()

[Greg Kroah-Hartman]

On Fri, May 26, 2017 at 11:40:33PM -0400, Oleg Drokin wrote:
> lov_getstripe() calls set_fs(KERNEL_DS) so that it can handle a struct
> lov_user_md pointer from user- or kernel-space.  This changes the
> behavior of copy_from_user() on SPARC and may result in a misaligned
> access exception which in turn oopses the kernel.  In fact the
> relevant argument to lov_getstripe() is never called with a
> kernel-space pointer and so changing the address limits is unnecessary
> and so we remove the calls to save, set, and restore the address
> limits.
> 
> Signed-off-by: John L. Hammond <john.hammond@intel.com>
> Reviewed-on: http://review.whamcloud.com/6150
> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3221
> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
> Reviewed-by: Li Wei <wei.g.li@intel.com>
> Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
> ---
>  drivers/staging/lustre/lustre/lov/lov_pack.c | 9 ---------
>  1 file changed, 9 deletions(-)

So is this the patch that you want applied to the staging tree(s) as
well?  If so, please let me know, otherwise I have no clue...

Come on, you know better than this...

greg k-h

Re: [PATCH] staging/lustre/lov: remove set_fs() call from lov_getstripe()

[Oleg Drokin]

On May 29, 2017, at 10:28 AM, Greg Kroah-Hartman wrote:

> On Fri, May 26, 2017 at 11:40:33PM -0400, Oleg Drokin wrote:
>> lov_getstripe() calls set_fs(KERNEL_DS) so that it can handle a struct
>> lov_user_md pointer from user- or kernel-space.  This changes the
>> behavior of copy_from_user() on SPARC and may result in a misaligned
>> access exception which in turn oopses the kernel.  In fact the
>> relevant argument to lov_getstripe() is never called with a
>> kernel-space pointer and so changing the address limits is unnecessary
>> and so we remove the calls to save, set, and restore the address
>> limits.
>> 
>> Signed-off-by: John L. Hammond <john.hammond@intel.com>
>> Reviewed-on: http://review.whamcloud.com/6150
>> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3221
>> Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
>> Reviewed-by: Li Wei <wei.g.li@intel.com>
>> Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
>> ---
>> drivers/staging/lustre/lustre/lov/lov_pack.c | 9 ---------
>> 1 file changed, 9 deletions(-)
> 
> So is this the patch that you want applied to the staging tree(s) as
> well?  If so, please let me know, otherwise I have no clue…

Yes, this is it.
Thanks!