Re: [PATCH] net: Revert "fib_trie: use seq_file_net rather than seq->private"

From: Sergei Shtylyov
Date: Wed Jun 04 2014 - 18:11:52 EST


On 06/05/2014 02:02 AM, Sasha Levin wrote:

This reverts commit 30f38d2fdd79f13fc929489f7e6e517b4a4bfe63.

fib_triestat is surrounded by a big lie: while it claims that it's a
seq_file (fib_triestat_seq_open, fib_triestat_seq_show), it isn't:

static const struct file_operations fib_triestat_fops = {
.owner = THIS_MODULE,
.open = fib_triestat_seq_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release_net,
};

Yes, fib_triestat is just a regular file.

A small detail (assuming CONFIG_NET_NS=y) is that while for seq_files
you could do seq_file_net() to get the net ptr, doing so for a regular
file would be wrong and would dereference an invalid pointer.

The fib_triestat lie claimed a victim, and trying to show the file would
be bad for the kernel. This patch just reverts the issue and fixes
fib_triestat, which still needs a rewrite to either be a seq_file or
stop claiming it is.

Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
net/ipv4/fib_trie.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 243c7f4..5afeb5a 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2166,7 +2166,7 @@ static void fib_table_print(struct seq_file *seq, struct fib_table *tb)

static int fib_triestat_seq_show(struct seq_file *seq, void *v)
{
- struct net *net = seq_file_net(seq);
+ struct net *net = (struct net *)seq->private;

'void *' doesn't need any explicit casting to another pointer type, the cast it automatic.

WBR, Sergei

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