patch "staging/lustre/lov: remove set_fs() call from lov_getstripe()" added to staging-linus

This is a note to let you know that I've just added the patch titled

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

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Oleg Drokin <[email protected]>
Date: Fri, 26 May 2017 23:40:33 -0400
Subject: staging/lustre/lov: remove set_fs() call from lov_getstripe()

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.

Reviewed-on: http://review.whamcloud.com/6150
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3221

---
 drivers/staging/lustre/lustre/lov/lov_pack.c | 9 ---------
 1 file changed, 9 deletions(-)

index 2e1bd47337fd..e6727cefde05 100644
@@ -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;
 }

2.13.0