vfs: introduce FMODE_UNSIGNED_OFFSET for allowing negative f_pos
Now, rw_verify_area() checsk f_pos is negative or not. And if negative,
returns -EINVAL.
But, some special files as /dev/(k)mem and /proc/<pid>/mem etc.. has
negative offsets. And we can't do any access via read/write to the
file(device).
So introduce FMODE_UNSIGNED_OFFSET to allow negative file offsets.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index dc5d5f5..fb2a5ab 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -771,6 +771,8 @@
static int mem_open(struct inode* inode, struct file* file)
{
file->private_data = (void*)((long)current->self_exec_id);
+ /* OK to pass negative loff_t, we can catch out-of-range */
+ file->f_mode |= FMODE_UNSIGNED_OFFSET;
return 0;
}