Commit 623c8d5c authored Jan 24, 2020 by David S. Miller

Merge branch 'netdev-seq_file-next-functions-should-increase-position-index'

Vasily Averin says:

====================
netdev: seq_file .next functions should increase position index

In Aug 2018 NeilBrown noticed
commit 1f4aace6 ("fs/seq_file.c: simplify seq_file iteration code and interface")
"Some ->next functions do not increment *pos when they return NULL...
Note that such ->next functions are buggy and should be fixed.
A simple demonstration is

dd if=/proc/swaps bs=1000 skip=1

Choose any block size larger than the size of /proc/swaps.  This will
always show the whole last line of /proc/swaps"

Described problem is still actual. If you make lseek into middle of last output line
following read will output end of last line and whole last line once again.

$ dd if=/proc/swaps bs=1  # usual output
Filename				Type		Size	Used	Priority
/dev/dm-0                               partition	4194812	97536	-2
104+0 records in
104+0 records out
104 bytes copied

$ dd if=/proc/swaps bs=40 skip=1    # last line was generated twice
dd: /proc/swaps: cannot skip to specified offset
v/dm-0                               partition	4194812	97536	-2
/dev/dm-0                               partition	4194812	97536	-2
3+1 records in
3+1 records out
131 bytes copied

There are lot of other affected files, I've found 30+ including
/proc/net/ip_tables_matches and /proc/sysvipc/*

This patch-set fixes files related to netdev@

https://bugzilla.kernel.org/show_bug.cgi?id=206283


====================

Signed-off-by: David S. Miller <davem@davemloft.net>

parents 2bec445f 4fc427e0

drivers/net/ethernet/chelsio/cxgb4/cxgb4_debugfs.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -70,8 +70,7 @@ static void seq_tab_start(struct seq_file seq, loff_t *pos)
		static void seq_tab_next(struct seq_file seq, void v, loff_t pos)
		{
		v = seq_tab_get_idx(seq->private, *pos + 1);
		if (v)
		++*pos;
		++(*pos);
		return v;
		}

drivers/net/ethernet/chelsio/cxgb4/l2t.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -678,8 +678,7 @@ static void l2t_seq_start(struct seq_file seq, loff_t *pos)
		static void l2t_seq_next(struct seq_file seq, void v, loff_t pos)
		{
		v = l2t_get_idx(seq, *pos);
		if (v)
		++*pos;
		++(*pos);
		return v;
		}

net/atm/proc.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -134,7 +134,6 @@ static void vcc_seq_stop(struct seq_file seq, void v)
		static void vcc_seq_next(struct seq_file seq, void v, loff_t pos)
		{
		v = vcc_walk(seq, 1);
		if (v)
		(*pos)++;
		return v;
		}

net/core/neighbour.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -3290,6 +3290,7 @@ static void neigh_stat_seq_next(struct seq_file seq, void v, loff_t pos)
		*pos = cpu+1;
		return per_cpu_ptr(tbl->stats, cpu);
		}
		(*pos)++;
		return NULL;
		}

net/ipv4/route.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -271,6 +271,7 @@ static void rt_cpu_seq_next(struct seq_file seq, void v, loff_t pos)
		*pos = cpu+1;
		return &per_cpu(rt_cache_stat, cpu);
		}
		(*pos)++;
		return NULL;

		}

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