slip: make slhc_free() silently accept an error pointer

BugLink: https://bugs.launchpad.net/bugs/1838459
commit baf76f0c58aec435a3a864075b8f6d8ee5d1f17e upstream.

This way, slhc_free() accepts what slhc_init() returns, whether that is
an error or not.

In particular, the pattern in sl_alloc_bufs() is

        slcomp = slhc_init(16, 16);
        ...
        slhc_free(slcomp);

for the error handling path, and rather than complicate that code, just
make it ok to always free what was returned by the init function.

That's what the code used to do before commit 4ab42d78e37a ("ppp, slip:
Validate VJ compression slot parameters completely") when slhc_init()
just returned NULL for the error case, with no actual indication of the
details of the error.

Reported-by: syzbot+45474c076a4927533d2e@syzkaller.appspotmail.com
Fixes: 4ab42d78e37a ("ppp, slip: Validate VJ compression slot parameters completely")
Acked-by: Ben Hutchings <ben@decadent.org.uk>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/net/slip/slhc.c b/drivers/net/slip/slhc.c
index f4e93f5fc2043ebb29c5b36e94afe49ec0c7d7ba..ea90db3c77058b6a799245bd5a3ff9f672b5da5e 100644 (file)
--- a/drivers/net/slip/slhc.c
+++ b/drivers/net/slip/slhc.c
@@ -153,7 +153,7 @@ out_fail:
 void
 slhc_free(struct slcompress *comp)
 {
-       if ( comp == NULLSLCOMPR )
+       if ( IS_ERR_OR_NULL(comp) )
                return;
 
        if ( comp->tstate != NULLSLSTATE )