From: Steven Rostedt <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx: simplification suggested by hpa]
[hpa@xxxxxxxxx: fix count==0 handling]
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/libfs.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff -puN fs/libfs.c~libfs-make-simple_read_from_buffer-conventional fs/libfs.c
--- a/fs/libfs.c~libfs-make-simple_read_from_buffer-conventional
+++ a/fs/libfs.c
@@ -527,14 +527,18 @@ ssize_t simple_read_from_buffer(void __u
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;
}
_
--
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