The patch titled
seq_file(): fix bug when seq_read() reads nothing
has been removed from the -mm tree. Its filename was
seq_file-fix-bug-when-seq_read-reads-nothing.patch
This patch was dropped because an alternative patch was merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: seq_file(): fix bug when seq_read() reads nothing
From: Bian Naimeng <biannm@xxxxxxxxxxxxxx>
When I used seq_file to read a proc file, I got a bug in seq_read(). If
show() skips the first element or the size of first element is 0, and the
size of second element is larger than the seq_file->size at the same time,
seq_read will return 0, so nothing can be read from the proc file.
So, if seq_read() returns because it finds the element is bigger than the
m->buf, it must make sure that either some date was filled to m->buf by
show(), or some data was flushed to the user buf beforehand. If not, it
should increase the m->buf until it can read this element.
[akpm@xxxxxxxxxxxxxxxxxxxx: fix comment]
Signed-off-by: Bian Naimeng <biannm@xxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/seq_file.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff -puN fs/seq_file.c~seq_file-fix-bug-when-seq_read-reads-nothing fs/seq_file.c
--- a/fs/seq_file.c~seq_file-fix-bug-when-seq_read-reads-nothing
+++ a/fs/seq_file.c
@@ -107,6 +107,7 @@ ssize_t seq_read(struct file *file, char
if (!size)
goto Done;
}
+First_record:
/* we need at least one record in buffer */
while (1) {
pos = m->index;
@@ -145,8 +146,18 @@ Fill:
err = m->op->show(m, p);
if (m->count == m->size || err) {
m->count = offs;
- if (likely(err <= 0))
+ if (err < 0)
break;
+ /*
+ * If no data was flushed to the user buf and nothing
+ * was read by show() beforehand, we should advance the
+ * m->buf until it can read this element.
+ */
+ if (err == 0 && m->count == 0 && copied == 0) {
+ m->index = next;
+ m->op->stop(m, p);
+ goto First_record;
+ }
}
pos = next;
}
_
Patches currently in -mm which might be from biannm@xxxxxxxxxxxxxx are
seq_file-fix-bug-when-seq_read-reads-nothing.patch
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