linux-kernel - [patch v2] sunrpc: integer underflow in rsc

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Message-ID: <20150224153401.GA12218@mwanda>
Date:	Tue, 24 Feb 2015 18:34:01 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Trond Myklebust <trond.myklebust@...marydata.com>,
	Anna Schumaker <anna.schumaker@...app.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jeff Layton <jlayton@...marydata.com>,
	Kinglong Mee <kinglongmee@...il.com>,
	linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Wang YanQing <udknight@...il.com>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [patch v2] sunrpc: integer underflow in rsc_parse()

If we call groups_alloc() with invalid values then it's might lead to
memory corruption.  For example, with a negative value then we might not
allocate enough for sizeof(struct group_info).

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
v2:  In v1, I changed groups_alloc().  The other places which call
groups_alloc() check the value before calling.  Eric wanted that, either
have all the callers check, or all the callers rely on groups_alloc().
In the end, Bruce Fields said adding the check here was probably
reasonable.

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 224a82f..1095be9 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -463,6 +463,8 @@ static int rsc_parse(struct cache_detail *cd,
 		/* number of additional gid's */
 		if (get_int(&mesg, &N))
 			goto out;
+		if (N < 0 || N > NGROUPS_MAX)
+			goto out;
 		status = -ENOMEM;
 		rsci.cred.cr_group_info = groups_alloc(N);
 		if (rsci.cred.cr_group_info == NULL)
--
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