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libfs: make simple_read_from_buffer conventional

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Impact: have simple_read_from_buffer conform to standards

It was brought to my attention by Andrew Morton, Theodore Tso, and H.
Peter Anvin that a read from userspace should only return -EFAULT if
nothing was actually read.

Looking at the simple_read_from_buffer I noticed that this function does
not conform to that rule.  This patch fixes that function.

[akpm@linux-foundation.org: simplification suggested by hpa]
[hpa@zytor.com: fix count==0 handling]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Steven Rostedt 2009-09-18 13:05:42 -07:00 committed by Al Viro
parent 94a8d5caba
commit 14be27460e
1 changed files with 6 additions and 2 deletions
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8
fs/libfs.c
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@ -527,14 +527,18 @@ ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos,
const void *from, size_t available)
{
loff_t pos = *ppos;
size_t ret;
if (pos < 0)
return -EINVAL;
if (pos >= available)
if (pos >= available || !count)
return 0;
if (count > available - pos)
count = available - pos;
if (copy_to_user(to, from + pos, count))
ret = copy_to_user(to, from + pos, count);
if (ret == count)
return -EFAULT;
count -= ret;
*ppos = pos + count;
return count;
}