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scsi: sg: sg_read(): simplify reading ->pack_id of userland sg_io_hdr_t

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We don't need to allocate a temporary buffer and read the entire structure
in it, only to fetch a single field and free what we'd allocated.  Just use
get_user() and be done with it...

Link: https://lore.kernel.org/r/20191017193925.25539-4-viro@ZenIV.linux.org.uk
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Al Viro 2019-10-17 20:39:21 +01:00 committed by Martin K. Petersen
parent 062c9d4527
commit c35a5cfb41
1 changed files with 2 additions and 11 deletions
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13
drivers/scsi/sg.c
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@ -441,17 +441,8 @@ 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) {
sg_io_hdr_t *new_hdr;
new_hdr = kmalloc(SZ_SG_IO_HDR, GFP_KERNEL);
if (!new_hdr) {
retval = -ENOMEM;
goto free_old_hdr;
}
retval =__copy_from_user
(new_hdr, buf, SZ_SG_IO_HDR);
req_pack_id = new_hdr->pack_id;
kfree(new_hdr);
if (retval) {
sg_io_hdr_t __user *p = (void __user *)buf;
if (get_user(req_pack_id, &p->pack_id)) {
retval = -EFAULT;
goto free_old_hdr;
}