[PATCH] scsi: avoid a double-fetch and a redundant copy

[Kangjie Lu]

What we need is only "pack_id", so do not create a heap object or copy
the whole object in. The fix efficiently copies "pack_id" only.

Signed-off-by: Kangjie Lu <k...@umn.edu>
---
 drivers/scsi/sg.c   |  4 ++--
 kernel/sched/core.c | 18 ++++++++++++------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 41774e4f9508..75842ceabc7f 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -446,8 +446,8 @@ sg_read(struct file *filp, char __user *buf, size_t count, 
loff_t * ppos)
                }
                if (old_hdr->reply_len < 0) {
                        if (count >= SZ_SG_IO_HDR) {
-                               retval = get_user(req_pack_id,
-                                               &((sg_io_hdr_t *)buf->pack_id));
+                               retval =
+                                       get_user(req_pack_id, &(sg_io_hdr_t 
__user *)buf->pack_id);
                                if (retval) {
                                        retval = -EFAULT;
                                        goto free_old_hdr;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6fedf3a98581..0a55bdce9a42 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4447,7 +4447,7 @@ do_sched_setscheduler(pid_t pid, int policy, struct 
sched_param __user *param)
  */
 static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr 
*attr)
 {
-       u32 size;
+       u32 size, size_cp;
        int ret;
 
        if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
@@ -4460,15 +4460,17 @@ static int sched_copy_attr(struct sched_attr __user 
*uattr, struct sched_attr *a
        if (ret)
                return ret;
 
+       size_cp = size;
+
        /* Bail out on silly large: */
        if (size > PAGE_SIZE)
                goto err_size;
 
        /* ABI compatibility quirk: */
        if (!size)
-               size = SCHED_ATTR_SIZE_VER0;
+               size_cp = SCHED_ATTR_SIZE_VER0;
 
-       if (size < SCHED_ATTR_SIZE_VER0)
+       else if (size < SCHED_ATTR_SIZE_VER0)
                goto err_size;
 
        /*
@@ -4483,7 +4485,7 @@ static int sched_copy_attr(struct sched_attr __user 
*uattr, struct sched_attr *a
                unsigned char val;
 
                addr = (void __user *)uattr + sizeof(*attr);
-               end  = (void __user *)uattr + size;
+               end  = (void __user *)uattr + size_cp;
 
                for (; addr < end; addr++) {
                        ret = get_user(val, addr);
@@ -4492,13 +4494,17 @@ static int sched_copy_attr(struct sched_attr __user 
*uattr, struct sched_attr *a
                        if (val)
                                goto err_size;
                }
-               size = sizeof(*attr);
+               size_cp = sizeof(*attr);
        }
 
-       ret = copy_from_user(attr, uattr, size);
+       ret = copy_from_user(attr, uattr, size_cp);
        if (ret)
                return -EFAULT;
 
+       /* Sanity check if size was changed in user space */
+       if (attr->size != size)
+               return -EINVAL;
+
        /*
         * XXX: Do we want to be lenient like existing syscalls; or do we want
         * to be strict and return an error on out-of-bounds values?
-- 
2.17.2 (Apple Git-113)