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Subject[PATCH] net/ipv4: Eliminate kstrdup memory leak
Date
The string clone is only used as a temporary copy of the argument val
within the while loop, and so it should be freed before leaving the
function. The call to strsep, however, modifies clone, so a pointer to the
front of the string is kept in saved_clone, to make it possible to free it.

The sematic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
local idexpression x;
expression E;
identifier l;
statement S;
@@

*x= \(kasprintf\|kstrdup\)(...);
...
if (x == NULL) S
... when != kfree(x)
when != E = x
if (...) {
<... when != kfree(x)
* goto l;
...>
* return ...;
}
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>

---
net/ipv4/tcp_cong.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 0ec9bd0..850c737 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -196,10 +196,10 @@ void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
int tcp_set_allowed_congestion_control(char *val)
{
struct tcp_congestion_ops *ca;
- char *clone, *name;
+ char *saved_clone, *clone, *name;
int ret = 0;

- clone = kstrdup(val, GFP_USER);
+ saved_clone = clone = kstrdup(val, GFP_USER);
if (!clone)
return -ENOMEM;

@@ -226,6 +226,7 @@ int tcp_set_allowed_congestion_control(char *val)
}
out:
spin_unlock(&tcp_cong_list_lock);
+ kfree(saved_clone);

return ret;
}


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