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From: Wu Fengguang on 6 Feb 2010 22:50
So as to return a uniform error -EOVERFLOW instead of a random one:

# kmem-seek 0xfffffffffffffff0
seek /dev/kmem: Device or resource busy
# kmem-seek 0xfffffffffffffff1
seek /dev/kmem: Block device required

Suggested by OGAWA Hirofumi.

CC: OGAWA Hirofumi <hirofumi(a)mail.parknet.co.jp>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu(a)intel.com>
---
drivers/char/mem.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)

--- linux.orig/drivers/char/mem.c 2010-01-15 09:11:25.000000000 +0800
+++ linux/drivers/char/mem.c 2010-01-20 09:45:55.000000000 +0800
@@ -700,16 +700,23 @@ static loff_t memory_lseek(struct file *

mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
switch (orig) {
- case 0:
+ case SEEK_CUR:
+ offset += file->f_pos;
+ if ((unsigned long long)offset <
+ (unsigned long long)file->f_pos) {
+ ret = -EOVERFLOW;
+ break;
+ }
+ case SEEK_SET:
+ /* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
+ if ((unsigned long long)offset >= ~0xFFFULL) {
+ ret = -EOVERFLOW;
+ break;
+ }
file->f_pos = offset;
ret = file->f_pos;
force_successful_syscall_return();
break;
- case 1:
- file->f_pos += offset;
- ret = file->f_pos;
- force_successful_syscall_return();
- break;
default:
ret = -EINVAL;
}


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