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| author | Guillaume Nault <g.nault@alphalink.fr> | 2018-04-19 16:20:48 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-04-22 14:46:35 -0400 |
| commit | 5411b6187adf62909e3b998ac782e722904c7487 (patch) | |
| tree | 6436022361ecbc67d743c3aa22e00696b1ce71f2 /net/l2tp | |
| parent | 353697e6e688c361af71fe921b89bbe71189d0ce (diff) | |
| download | linux-5411b6187adf62909e3b998ac782e722904c7487.tar.bz2 | |
l2tp: fix {pppol2tp, l2tp_dfs}_seq_stop() in case of seq_file overflow
Commit 0e0c3fee3a59 ("l2tp: hold reference on tunnels printed in pppol2tp proc file")
assumed that if pppol2tp_seq_stop() was called with non-NULL private
data (the 'v' pointer), then pppol2tp_seq_start() would not be called
again. It turns out that this isn't guaranteed, and overflowing the
seq_file's buffer in pppol2tp_seq_show() is a way to get into this
situation.
Therefore, pppol2tp_seq_stop() needs to reset pd->tunnel, so that
pppol2tp_seq_start() won't drop a reference again if it gets called.
We also have to clear pd->session, because the rest of the code expects
a non-NULL tunnel when pd->session is set.
The l2tp_debugfs module has the same issue. Fix it in the same way.
Fixes: 0e0c3fee3a59 ("l2tp: hold reference on tunnels printed in pppol2tp proc file")
Fixes: f726214d9b23 ("l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp')
| -rw-r--r-- | net/l2tp/l2tp_debugfs.c | 5 | ||||
| -rw-r--r-- | net/l2tp/l2tp_ppp.c | 5 |
2 files changed, 8 insertions, 2 deletions
diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c index b8f9d45bfeb1..7f1e842ef05a 100644 --- a/net/l2tp/l2tp_debugfs.c +++ b/net/l2tp/l2tp_debugfs.c @@ -106,8 +106,11 @@ static void l2tp_dfs_seq_stop(struct seq_file *p, void *v) return; /* Drop reference taken by last invocation of l2tp_dfs_next_tunnel() */ - if (pd->tunnel) + if (pd->tunnel) { l2tp_tunnel_dec_refcount(pd->tunnel); + pd->tunnel = NULL; + pd->session = NULL; + } } static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v) diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c index 7d0c963680e6..1404bc1c1bb7 100644 --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -1618,8 +1618,11 @@ static void pppol2tp_seq_stop(struct seq_file *p, void *v) return; /* Drop reference taken by last invocation of pppol2tp_next_tunnel() */ - if (pd->tunnel) + if (pd->tunnel) { l2tp_tunnel_dec_refcount(pd->tunnel); + pd->tunnel = NULL; + pd->session = NULL; + } } static void pppol2tp_seq_tunnel_show(struct seq_file *m, void *v) |