[PATCH 3.15 069/109] net: ppp: fix creating PPP pass and active filters

Greg Kroah-Hartman
2014-07-26T19:02:31Z

From: Christoph Schulz <develop@kristov.de>

[ Upstream commit cc25eaae238ddd693aa5eaa73e565d8ff4915f6e ]

Commit 568f194e8bd16c353ad50f9ab95d98b20578a39d ("net: ppp: use
sk_unattached_filter api") inadvertently changed the logic when setting
PPP pass and active filters. This applies to both the generic PPP subsystem
implemented by drivers/net/ppp/ppp_generic.c and the ISDN PPP subsystem
implemented by drivers/isdn/i4l/isdn_ppp.c. The original code in ppp_ioctl()
(or isdn_ppp_ioctl(), resp.) handling PPPIOCSPASS and PPPIOCSACTIVE allowed to
remove a pass/active filter previously set by using a filter of length zero.
However, with the new code this is not possible anymore as this case is not
explicitly checked for, which leads to passing NULL as a filter to
sk_unattached_filter_create(). This results in returning EINVAL to the caller.

Additionally, the variables ppp->pass_filter and ppp->active_filter (or
is->pass_filter and is->active_filter, resp.) are not reset to NULL, although
the filters they point to may have been destroyed by
sk_unattached_filter_destroy(), so in this EINVAL case dangling pointers are
left behind (provided the pointers were previously non-NULL).

This patch corrects both problems by checking whether the filter passed is
empty or non-empty, and prevents sk_unattached_filter_create() from being
called in the first case. Moreover, the pointers are always reset to NULL
as soon as sk_unattached_filter_destroy() returns.

Signed-off-by: Christoph Schulz <develop@kristov.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/isdn/i4l/isdn_ppp.c | 20 ++++++++++++++++----
drivers/net/ppp/ppp_generic.c | 22 ++++++++++++++++------
2 files changed, 32 insertions(+), 10 deletions(-)

--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -644,9 +644,15 @@ isdn_ppp_ioctl(int min, struct file *fil
fprog.len = len;
fprog.filter = code;

- if (is->pass_filter)
+ if (is->pass_filter) {
sk_unattached_filter_destroy(is->pass_filter);
- err = sk_unattached_filter_create(&is->pass_filter, &fprog);
+ is->pass_filter = NULL;
+ }
+ if (fprog.filter != NULL)
+ err = sk_unattached_filter_create(&is->pass_filter,
+ &fprog);
+ else
+ err = 0;
kfree(code);

return err;
@@ -663,9 +669,15 @@ isdn_ppp_ioctl(int min, struct file *fil
fprog.len = len;
fprog.filter = code;

- if (is->active_filter)
+ if (is->active_filter) {
sk_unattached_filter_destroy(is->active_filter);
- err = sk_unattached_filter_create(&is->active_filter, &fprog);
+ is->active_filter = NULL;
+ }
+ if (fprog.filter != NULL)
+ err = sk_unattached_filter_create(&is->active_filter,
+ &fprog);
+ else
+ err = 0;
kfree(code);

return err;
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -763,10 +763,15 @@ static long ppp_ioctl(struct file *file,
};

ppp_lock(ppp);
- if (ppp->pass_filter)
+ if (ppp->pass_filter) {
sk_unattached_filter_destroy(ppp->pass_filter);
- err = sk_unattached_filter_create(&ppp->pass_filter,
- &fprog);
+ ppp->pass_filter = NULL;
+ }
+ if (fprog.filter != NULL)
+ err = sk_unattached_filter_create(&ppp->pass_filter,
+ &fprog);
+ else
+ err = 0;
kfree(code);
ppp_unlock(ppp);
}
@@ -784,10 +789,15 @@ static long ppp_ioctl(struct file *file,
};

ppp_lock(ppp);
- if (ppp->active_filter)
+ if (ppp->active_filter) {
sk_unattached_filter_destroy(ppp->active_filter);
- err = sk_unattached_filter_create(&ppp->active_filter,
- &fprog);
+ ppp->active_filter = NULL;
+ }
+ if (fprog.filter != NULL)
+ err = sk_unattached_filter_create(&ppp->active_filter,
+ &fprog);
+ else
+ err = 0;
kfree(code);
ppp_unlock(ppp);
}