linux-kernel - [PATCH 3.16 114/157] slip: make slhc_free() silently accept an error pointer

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Message-ID: <lsq.1565469607.349357644@decadent.org.uk>
Date:   Sat, 10 Aug 2019 21:40:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        syzbot+45474c076a4927533d2e@...kaller.appspotmail.com,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "David Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 114/157] slip: make slhc_free() silently accept an
 error pointer

3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

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@...kaller.appspotmail.com
Fixes: 4ab42d78e37a ("ppp, slip: Validate VJ compression slot parameters completely")
Acked-by: Ben Hutchings <ben@...adent.org.uk>
Cc: David Miller <davem@...emloft.net>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/slip/slhc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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 )