linux-kernel - [PATCH] ppp: fix out-of-bounds access in bpf_prog

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Date:   Wed,  4 Dec 2019 21:54:19 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>, Al Viro <viro@...iv.linux.org.uk>
Cc:     Paul Mackerras <paulus@...ba.org>, bpf@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-ppp@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot <syzbot+eb853b51b10f1befa0b7@...kaller.appspotmail.com>,
        syzkaller-bugs@...glegroups.com
Subject: [PATCH] ppp: fix out-of-bounds access in bpf_prog_create()

From: Eric Biggers <ebiggers@...gle.com>

sock_fprog_kern::len is in units of struct sock_filter, not bytes.

Fixes: 3e859adf3643 ("compat_ioctl: unify copy-in of ppp filters")
Reported-by: syzbot+eb853b51b10f1befa0b7@...kaller.appspotmail.com
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 drivers/net/ppp/ppp_generic.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 0cb1c2d0a8bc..3bf8a8b42983 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -564,8 +564,9 @@ static struct bpf_prog *get_filter(struct sock_fprog *uprog)
 		return NULL;
 
 	/* uprog->len is unsigned short, so no overflow here */
-	fprog.len = uprog->len * sizeof(struct sock_filter);
-	fprog.filter = memdup_user(uprog->filter, fprog.len);
+	fprog.len = uprog->len;
+	fprog.filter = memdup_user(uprog->filter,
+				   uprog->len * sizeof(struct sock_filter));
 	if (IS_ERR(fprog.filter))
 		return ERR_CAST(fprog.filter);
 
-- 
2.24.0